In addition to being a popular host, Bill was also a popular celebrity guest on just about every game show that needed one.  One of the more intelligent game players, Bill usually won most any game he played and still managed to be witty and funny doing it.  Plus he always looked like he was having such a good time!

This list is of Bill's appearances as a guest on various game shows, including a couple of times when he appeared only to plug his own show and not to play.

Sources for the list below include TV Guide listings, vintage newspaper articles, references and pictures in The Encyclopedia of TV Game Shows, tapes that exist in the collections of game show traders and several internet game show databases.  Brendan McLaughlin has been very generous in sharing his own research and TV Guide listings.  Kenneth Johannessen, Chris Tufts and Marshall Akers were able to add several items as well.  Your specific additions are welcome.
The only reason this list isn't even longer is that throughout the seventies, most game shows were based in California while Bill was still working in New York.  Appearances on those west coast shows were limited to occasional visits during breaks in his own schedule. For example, in a short trip to L.A. in July, 1975, Bill taped appearances as a celebrity guest on Tattletales, Rhyme and Reason and You Don't Say.
THE $10,000 PYRAMID (Dick Clark)          
    August 13-17, 1973 with Fannie Flagg
          (Some sources say this week may have been delayed by a week or so.) 
    January 28-February 1, 1974 with Anita Gillette  
    March 3-7, 1975 with Jo Anne Worley           
    August 18-22, 1975 with Lee Meriwether           
    October 13-17, 1975 with Stephanie Braxton          
THE $20,000 PYRAMID (Dick Clark)           
    January 19-23, 1976 with Jo Anne Worley (first week with larger prize)  
    March 29-April 2, 1976 with Anita Gillette           
    July 12-16, 1976 with Barbara Feldon 
    December 13-17, 1976 with Anita Gillette  
    September 27-October 1, 1976 with Anne Meara           
    August 8-12, 1977 with Lucie Arnaz           
    December 12-16, 1977 with Caren Kaye           
    December 4-8, 1978 with Lynn Redgrave           
    March 5-9, 1979 with Anne Meara           
    July 23-27, 1979 with Adrienne Barbeau           
    June 23-27, 1980 with Lois Nettleton (final week of series)           
 THE $25,000 PYRAMID (Dick Clark)           
    October 10-14, 1983 with Shelley Smith           
    March 11-15, 1985 with Jo Anne Worley           
    March 24-28, 1986 with Elaine Joyce           
    July 21-25, 1986 with Lois Nettleton           
    June 1-5, 1987 with Betty White (Bill's last TV appearance)            

ALL-STAR SECRETS (Bob Eubanks)     
    Feb 26-March 2, 1979 with Nanette Fabray, Arte Johnson, Della Reese and John Schuck     

BREAK THE BANK (Bert Parks)           
    Bill filled in as host during Parks' vacation in August, 1954.          

BREAK THE BANK (Jack Barry)   
Syndicated.  Specific dates varied.         
    1976 with Barbara Eden, Joey Bishop, William Conrad, Abe Vigoda, Bob Crane, Jaye P. Morgan, Lee Meriwether and Anson Williams 
BREAK THE BANK (Tom Kennedy)         
     July 19-23, 1976 (final week of series) with Joyce Bulifant, Soupy Sales, Elke Sommer, Donny Most, Jo Anne Worley, Jan Murray, Jaye P. Morgan and Lonnie Schorr  
CARD SHARKS (Jim Perry)           
    September 8-26, 1980 three-week series featuring game show hosts, with Gene Rayburn, Wink Martindale, Jack Clark, Tom Kennedy, Jim Lange, Allen Ludden and Alex Trebek.    

    September 16-20, 1974 with Geoff Edwards, Carol Wayne, Jo Ann Pflug, Macdonald Carey and Pat Henry  
    April 26-30, 1976 with Lynn Anderson, Peter Brown, Dody Goodman, Dick Martin and Carol Wayne 
    July 12-16, 1976 with James Darren, Anne Meara, Paul Williams, Dick Gautier, and Carol Wayne 
    Fall, 1976 syndicated show with Dick Gautier, Arte Johnson, Lonnie Schorr, Carol Wayne, and Buddy Hackett.  

Eagle-eyed contributor Chris Tufts points out that during the week of July 12-16, 1976, Bill could be seen as a guest on three different shows on three different networks.  He was on Celebrity Sweepstakes (NBC), The $20,000 Pyramid (ABC) and Tattletales (CBS).
CONCENTRATION (Hugh Downs)           
    December 24, 1965 with Betty White          
Bill used this appearance to plug Eye Guess.  He also appeared on Concentration in 1971, not to play, but to plug the debut of Three on a Match.       
CROSS-WITS (Jack Clark)     
Syndicated.  Specific dates varied.         
Syndicated shows in the seventies, including many of the games listed here, were on tapes that were "bicycled" from one station to the next throughout the country.  Under that system, different markets saw different episodes of a given series on any given day.  That's why we can't be more specific about the air dates of those shows.  In today's system of satellite distribution, virtually all markets see the same episode of a syndicated show on the same day.
    1976 with Fannie Flagg, Patti Deutsch and Jack Carter    
    1977 with Fannie Flagg, Elaine Joyce and Rick Hurst    
    1977 with Dody Goodman, Joyce Bulifant and Ron Ely  
    1978 with Pat Carroll, Alice Ghostley, and Milt Kamen   
    1979 with Roxie Roker, Marcia Wallace and Bobby Goldsboro    
    1979 with Roxie Roker, Marcia Wallace and Fred Grandy     
    1979 with Vicki Lawrence, Polly Holliday and Don Galloway     
    1979 with Jo Anne Worley, Elinor Donahue and Johnny Brown     
FAMILY FEUD (Richard Dawson)           
    November, 1983 game show hosts week, with Bob Eubanks, Jim Perry, Nipsey Russell, Betty White, Tom Kennedy, Jim Lange, Peter Marshall, Bert Parks and Leslie Uggams.   
HE SAID, SHE SAID (Joe Garagiola)    
Syndicated.  Specific dates varied.  
    1969 with Gene Rayburn and others            
    1970 with Orson Bean, Robert Lansing and Heywood Hale Broun 
    1970 with Orson Bean, Patrick O'Neal, and Pat Carroll  
    1970 with Dick Clark, Peter Duchin, and Peter Lind Hayes & Mary Healy  
    1970 with Alejandro Rey, Genevieve, and Kyle Rote & Sharon Ritchie  
    1970 with Dick Clark, Jerry Shane, and Ruby Dee & Ossie Davis  
(Bill also substituted for Joe Garagiola as host on at least one occasion, possibly when Joe had a committment to baseball broadcasting.)           

HOLLYWOOD SQUARES (Peter Marshall) [NBC Daytime]         
    August 16-20, 1971 with Wally Cox, Rose Marie, Jack Klugman, Tony Randall, Karen Valentine, Jackie Vernon, Charley Weaver, and Carol Lawrence.         

JEOPARDY! (Art Fleming)           
    March 30, 1972 Eighth Anniversary Show with Peter Marshall and Art James           

LIARS CLUB (Allen Ludden)   
Syndicated.  Specific dates varied.            
    1978 with Larry Hovis, Dody Goodman and Alan Sues          
MATCH GAME (Gene Rayburn)          
    December 20-24, 1965 with Joan Rivers          
    May 15-19, 1967 with Phyllis Newman          
    December 18-22, 1967 with Bess Myerson          
    February 12-16, 1968 with Fannie Flagg          
    February 17-21, 1969 with Hugh Downs          

MATCH GAME '7X (Gene Rayburn)           
    Nov 12-16, 1973 with Brett Somers, Jack Klugman, Cass Elliott, Richard Dawson and Loretta Swit    
    March 28-April 3, 1974 with Brett Somers, Charles Nelson Reilly, Patty Deutsch, Richard Dawson and Betty White     
    *April 14-20, 1976 with Brett Somers, Charles Nelson Reilly, Janice Pennington, Richard Dawson and Fannie Flagg    
    *September 26-30, 1977 with Brett Somers, Charles Nelson Reilly, Debralee Scott, Richard Dawson and Fannie Flagg    
    *April 18-20, 1979 with Fred Grandy, Brett Somers, Charles Nelson Reilly, Connie Stevens and Marcia Wallace  
MATCH GAME (Gene Rayburn)  
Syndicated.  Specific dates varied.         
    *1979-80 week with Brett Somers, Charles Nelson Reilly, Lee Meriwether, Bill Daily and Betty White           
    *1980-81 week with Peter Marshall, Brett Somers, Dick Martin, Elaine Joyce and Betty White           
    1981-82 week with Jimmie Walker, Brett Somers, Charles Nelson Reilly, Lilibet Stern and Elaine Joyce           
    1981-82 week with Brett Somers, Charles Nelson Reilly, Sharon Farrell, Maclean Stevenson and Edie McClurg  
*A sixth show was taped during the starred weeks for the syndicated MATCH GAME PM.  
MATCH GAME/HOLLYWOOD SQUARES HOUR (Gene Rayburn & Jon Bauman)     
    January 16-20, 1984 with Brian Mitchell, Jay Leno, Linda Dano, Ellen Bry, Richard Kline, Lyle Waggoner, and Phyllis Diller.  

Bill appeared on The Match Game/ Hollywood Squares Hour with two little-known young celebrities who would go on to become much more famous.  In 1984, Jay Leno was a rising stand-up comic and Brian Mitchell was a supporting actor in a medical series.  Today, Leno is host of The Tonight Show and Mitchell is a Tony Award winning Broadway performer.
MINDREADERS (Dick Martin)          
    August 20-24, 1979 with Brett Somers          

PASSWORD (Allen Ludden) [60's CBS]          
    January 30, 1962 with Dorothy Collins            
    August 21, 1962 with Rita Moreno (Jack Clark hosts)            
    March 10, 1963 with Jane Fonda            
    July 8, 1963 with Susan Strasberg            
    November 1-5, 1965 daytime week with Florence Henderson            

PASSWORD (Allen Ludden) [70's ABC]          
    July 12-16, 1971 with Florence Henderson          
    November 12-16, 1973 with Helen Reddy          
    May 6-10, 1974 with Susan Oliver          

PASSWORD PLUS (Allen Ludden)           
    March 12-16, 1979 with Mary Tyler Moore           
    July 9-13, 1979 with Patty Duke           
    October 29-Novembeer 2, 1979 with Marcia Wallace           
    March 3-7, 1980 with Peggy Cass           
PASSWORD PLUS (Bill Cullen)           
(Bill hosted Password Plus for four weeks during Allen Ludden's illness.)           
    April 14-18, 1980 with Elaine Joyce and Bill Anderson           
    April 21-25, 1980 with Nanette Fabray and Skip Stephenson           
    April 28-May 2, 1980 with Vicki Lawrence and Dick Gautier           
    May 5-9, 1980 with Betty White and Greg Morris           
PASSWORD PLUS (Allen Ludden)           
    May 12-16, 1980 with Susan Richardson           
    July 29-August 4, 1980 with Betty White           
    October 14-20, 1980 with Karen Marrow           
PASSWORD PLUS (Tom Kennedy)           
    November 11-17, 1980 with Barbara Rhoades           
    December 31, 1980-January 7, 1981 with Susan Richardson           
    February 11-17, 1982 with Patty Duke Astin            
PERSONALITY (Larry Blyden)     
    July 10-14, 1967 with Joan Rivers and Henry Morgan (Second week of series)   
    August 21-25, 1967 with Phyllis Newman and Sheila MacRae     
    October 30-November 3, 1967 with Joan Fontaine and Betsy Palmer   
    December 4-8, 1967 with Florence Henderson and Selma Diamond   
    January 8-12, 1968 with Joan Bennett and Joan Rivers   
    February 26-March 1, 1968 with Totie Fields and Gig Young     
    April 15-19, 1968 with Sheila MacRae and Betsy Palmer     
    May 13-17, 1968 with Eva Gabor and Pat Carroll     
    June 24-28, 1968 with Carol Lawrence and Dick Shawn   
    October 21-25, 1968 with Pat Carroll and Lainie Kazan   
    March 24-28, 1969 with Betsy Palmer and Selma Diamond   
    August 18-22, 1969 with Julia Meade and Sheila MacRae   
THE PRICE IS RIGHT (Bob Barker)         
    Bill appeared on TPIR in 1982 to plug Child's Play.  No mention was made in his brief visit of his own history with The Price Is Right.         

RHYME AND REASON (Bob Eubanks)           
    August 4-8, 1975 with Jaye P. Morgan, Mitzi McCall, Meredith MacRae, Pat Harrington and Nipsey Russell          

SHOOT FOR THE STARS (Geoff Edwards)           
    January 10-14, 1977 with Penny Peyser          
    April 4-8, 1977 with Adrienne Barbeau          
    July 25-29, 1977 with Barbara Feldon          
    September 26-30, 1977 with Adrienne Barbeau (final week)          

SNAP JUDGMENT (Ed McMahon)          
    April 20-24, 1967 with Diana Sands          
    March 19-23, 1968 with Phyllis Kirk          
    November 28-December 2, 1968 with Jayne Meadows          
    March 17-21, 1969 with Dina Merrill          

STRIKE IT RICH (Warren Hull)   
    1954 Guest Host   
Found in only one source and not confirmed, though Hull used a number of guest hosts for his series (including Robert Alda, Monty Hall and Dom Ameche) so why not Bill?  Bill is also credited with participating in the RADIO version of the series.   

SUPER PASSWORD (Bert Convy)           
    October 22-26, 1984 with Marcia Wallace          
    February 4-8, 1985 with Marcia Wallace (Tournament of Champions)          
    September 16-20, 1985 with Tom Poston          
    January 27-31, 1986 with Kim Miyori          

TATTLETALES (Bert Convy)           
    March 25-29, 1974 with Allen Ludden & Betty White and Jo Ann Pflug & Chuck Woolery
    September 2-6. 1974 with Bill Macy and Bobby Van & Elaine Joyce   
    August 14-20, 1975 with Joan Collins and Zsa Zsa Gabor 
    July 12-16, 1976 with Judy Norton & Doug Taylor and Don & Susan Stewart 
    1977 week with Bob Barker, Patty Weaver  
    Aug 29-Sept 2, 1977 with Gary Collins & Mary Ann Mobley and Ray Buktenica & Joyce DeWitt 
    March 1-5, 1982 with Conrad Janis and Irlene Mandrell  
    September 9-13, 1982 with Stuart Damon and Christopher Norris  
    April 12-18, 1983 with Maureen Reagan and Phyllis Diller  

TO TELL THE TRUTH (Bud Collyer)           
    October 19, 1964 with Peggy Cass, Kitty Carlisle and Tom Poston  
    January 18, 1965 with IGAS panelists Betsy Palmer, Henry Morgan and Bess Myerson.  
TO TELL THE TRUTH (Robin Ward)  
Syndicated.  Specific dates varied.  The week numbers are the production weeks of the 39-week season.           
    Week 6 with Fannie Flagg, Soupy Sales and Peggy Cass 
    Week 7 with John Wade, Susan Lucci and Polly Bergen 
    Week 13 with John Wade, Tiiu Leek and Peggy Cass 
    Week 14 with Pat Collins, Dick Clark and Polly Bergen 
Bill was a regular on the 70s version of To Tell The Truth     

TRIVIA TRAP (Bob Eubanks)           
    1984 celeb week with Jamie Farr, Tom Poston, Vicki Lawrence, Betty White and Jayne Meadows.  
WHAT'S MY LINE? (John Charles Daly)  
    April 1, 1956 with fellow I've Got A Secret panelists Henry Morgan, Jayne Meadows and Faye Emerson collectively as Mystery Guests          
    July 9, 1961 as a solo Mystery Guest.  The panel (Dorothy Kilgallen, Bennett Cerf, Steve Allen and Jayne Meadows) failed to identify him.   
WHAT'S MY LINE? (Larry Blyden)   
    One source says Bill participated in this syndicated version of the series in 1974.  If true, it was probably as a Mystery Guest again, since according to the book What's My Line?, Bill was never a member of the panel. Not confirmed.   

WHEEL OF FORTUNE (Chuck Woolery)           
    Single appearance in 1980 as part of a special game show hosts week  Bill's episode does not survive (as far as we know), but the following day's with Tom Kennedy does.  At the end of Kennedy's show, he, Woolery and Susan Stafford comment on how well Bill performed the day before.         

YOU DON'T SAY (Tom Kennedy) [60s NBC Daytime]          
    April 8-12, 1968 with Pat Carroll          
    November 11-15, 1968 with Barbara Bain          
YOU DON'T SAY (Tom Kennedy) [70s ABC Daytime]          
    July 21-25, 1975 with Ann Elder, Joyce Bulifant, and Larry Hovis