Pac-Man, maybe the definitive arcade game. Certainly one of the game to which the industry owes the "golden years of arcade", an arcade boom during the 1980's and the growth of the games industry as such.
More importantly to us though, Pac-Man is the game which represents everything that's good about gaming (any kind of gaming) and nothing that is bad. It's easy to grasp but hard to master. Addictive and stuffed with pure unadulterated gameplay. Frustrating but always having you come back for more. Never boring and always tense, even for the best players. Always giving you the impression that you can master it but never quite letting you get there.
There are many great Pac-Man players out there but only one did eventually play the perfect game, and it took over 20 years of gamers around the world trying: On July 3rd 1999 Billy Mitchell scored 3,333,360 reached level 255 at which point the game locks up with the first life and became the worlds best known arcade player.