Hardcore Gaming 101 - Lemmings
Holy damn, that is a LOT of ports. The only game anywhere close to possibly overtaking that number is something like Pac-Man or Tetris. The concept is straightforward. The lemmings are trying to go somewhere that's not really explained what it is, and it's your job to guide them there.
DMA Design's classic puzzle game has you guiding a group of mindless rodents through tricks, traps, and other assorted dangers. Includes a look at all of the (many many) ports of the original game, plus its numerous successors, official and otherwise.