Pac-man and Ms. Pac-man for the Gameboy
The Tengen (Atari) versions of Pac-man, Pac-Mania, and Ms. Pac-man for the NES. All three are really pretty great games. I played a LOT of Pac-Mania on the NES.
We have the Genesis versions of Pac-Mania, Ms. Pac-man, and 'Pac-man 2 The New Adventure'. We enjoyed the NES and SNES versions more then the ones on the Genny.
The Neo-Geo Pocket had a great version of Pac-Man. We at the museum really liked the NGP. We have two of them and most of the games released in the US. It just couldn't compete with GameBoy and Pokemon.
Pac-man for the Famicom (Japanese NES), it plays just like the american one except the ghost's names are in Japanese.