A baseball game in which the pitcher allows no one from the opposing team to reach base, whether it be via hit, walk, error, hit batsman, etc. 27 batters up, 27 batters down. There have been 18 perfect games in major league history. (Note: there have been over 300 no-hitters)

                      PERFECT GAMES

Mark Buehrle          CHW vs. TAM    07/23/2009
Randy Johnson         ARZ vs. ATL    05/18/2004
David Cone            NYY vs. MON    07/18/1999
David Wells           NYY vs. MIN    05/17/1998
Kenny Rogers          TEX vs. CAL    07/28/1994
Dennis Martinez       MON vs. LAD    07/28/1991
Tom Browning          CIN vs. LAD    09/16/1988
Mike Witt             CAL vs. TEX    09/30/1984
Len Barker            CLE vs. TOR    05/15/1981
Jim "Catfish" Hunter  OAK vs. MIN    05/08/1968
Sandy Koufax          LA  vs. CHC    09/09/1965
Jim Bunning           PHI vs. NYG    06/21/1964
Don Larsen            NYY vs. BRK    10/08/1956 *
Charles Robertson     CHW vs. DET    04/30/1922
Addie Joss            CLE vs. CHW    10/02/1908 
Cy Young              BOS vs. PHI    03/05/1904
John Ward             PRO vs. BUF    06/17/1880 **
John Richmond         WOR vs. CLE    06/12/1880 **

*  Game 5 of the World Series
** Prior to the modern era

                 UNOFFICIAL PERFECT GAMES

Pedro Martinez        MON vs. SDP    06/03/1995 *
Harvey Haddix         PIT vs. MIL    05/26/1959 **
Ernie Shore           BOS vs. WAS    06/23/1917 ***

*   Pitched 9 perfect innings, allowed a leadoff double in 
    the 10th inning.
**  Pitched 12 perfect innings, lost in the 13th inning.
*** After Babe Ruth was ejected for arguing about a walk 
    issued to the first batter, Shore picked off the runner 
    and then set down the next 26 batters in order.

Perfect game, also called bowling 300: Bowling a strike in every frame of a bowling game (10 frames plus two bonus frames, for 12 total). A perfect game scores 300 points: 30 points for each of ten frames. This is the highest single-game score possible, and is the Holy Grail of bowling. Many bowling alleys prominently display the name of any bowler who has bowled a perfect game at that establishment.

Homer Simpson bowled a perfect game (s11e232); Al Bundy did not, but Peg Bundy did (s4e76); Ralph Kramden does not seem to have done so.

Perfect Game is a slot machine produced by WMS Gaming, (the gambling branch of Williams the arcade game manufacturer). This is an electronic slot machine, with a monitor instead of actual reels. The theme of this particluar machine is that of a bowling alley. This is a nine line machine with a total of 5 reels, and different versions will accept anywhere from 1 to 90 coins. This machine is usually takes 5 cent tokens, but some casinos have 25 cent and 1 dollar versions of this machine.

The symbols in this game are all bowling related, (balls, pins, bowlers, bowling bags, and similar items are most common). This game features three different bonuses. The first is the "gutter bonus". This is activated by getting 5 bowling pin symbols in a scatter pattern, (that means one on each reel). This will cause a bowling ball to appear on screen, and give you a small bonus. The second bonus is the "Perfect Game" bonus, (which is activated by getting 3 bowler faces). Which is an entire bowling video game all to its own, (you select a bowler, then bowl for up to five frames, or until you leave an open frame). The third bonus, ("Beat the Champ"), is quite rare. To get this one you have to beat a particular score in the "Perfect Game" bonus. I have never actually seen this last bonus, despite repeated trips to the casino.

This game, (like most electronic lot machines), gives the majority of its payout through the bonus round. You will find that your money quickly goes down the drain if you do not manage to hit the bonus round from time to time.

From the WMS Gaming website

Meet Bruno, Linda and Horace, your bowling team! You'll see their faces again and again on the reel symbols and in the bonus rounds of PERFECT GAME, the bowling-themed video slot machine from WMS Gaming. This 5-reel, 9-line video slot game features many first screen bonus features, where the slot player joins the bowling team to strike up some real action!

A game has a perfect game when there is a strategy that will allow you to never lose (i.e. always win or draw)

Is there always a perfect game?

Some games of course cannot be played perfectly. An example of this is Freecell. Despite the claims in the Windows help file that it is believed (but not proven) that it is possible to win every game, some deals are impossible. The first such deal to be found is number 11982 and was discovered in 1995.

Complete information games that are dynamic and finite have perfect games. This means that the players have a complete knowledge of the situation, that players take turns and that the game has a well defined end. In chess for example both of the players have all the information available to them: the positions of the pieces on the board. Chess without the draw by repetition rule or connect four without a limit on the number of rows, would be non finite. In poker information is not shared, players do not show each other their cards. Games like backgammon are not complete information games because players cannot know what the next dice roll will be. Lastly stone paper scissors is not dynamic, because both players make their move at the same time and their decision is revealed simultaneously.

There's a perfect game of chess? I'm off to play the world champion!

Finding how to play a perfect game is difficult. Although many games such as chess, checkers or go can in theory be played perfectly, the complexity and sheer number of possible moves of the games often puts a brute force approach far beyond the possibilities of current computers. Awari, a variant of mancala was recently solved, and an unbeatable opponent known as the Awari Oracle is now available. To gauge the scale of things, this program plays with the aid of a 778 gigabyte database of positions and moves. For some other games (notable checkers and othello) there have been some very good attempts.

Chinook for example is a checkers playing program developed by Dr. Jonathan Schaeffer, and is currently the world champion. It plays with a database of all possible positions with 8 or less pieces of the board (that's around 444 billion positions). You can play a cut down version of Chinook (the database has only positions with 6 pieces) at http://www.cs.ualberta.ca/~chinook/play.php. Ultimately the team hopes to completely solve the game.

Choose carefully...

For some games if both players play a perfect game then the result will be a draw. Noughts and crosses is such a game, with a simple strategy: go for the centre first, followed by the corners (unless of course you are forced to make a certain move to avoid losing). If both players do this, then the outcome will always be a draw, and you cannot beat someone playing this strategy. In other games a perfect game is playable by only one of the players. For example it has been shown that in connect four, if there is not the option of passing a turn, the player who moves first can always win. No matter what the second player does, they cannot win.

Finally a little puzzler: This little 2 player game starts with the numbers 2,3,4,5,6,7,8,9,10. Each player picks a number in turn, and once a number is picked it may not be picked again by either player. The aim of the game is to pick exactly three numbers whose sum is 18. It is possible for there to be a draw. Can you play a perfect game?

http://home.earthlink.net/~fomalhaut/fcfaq.html
http://www.ce.unipr.it/~gbe/velena.html
http://www.mathpuzzle.com/winways.htm