I was just recently thinking about how Pac-Man is available on pretty much every system out there in some form or another. So this question came up...how many different Pac-Mans do you own? This could be on a system, a TV Plug N Play system, a game compilation such as Namco Museum, an unlockable mini-game inside a larger game, or even the original arcade cabnet itself. As for me, I have 4 versions of Pac-Man and 2 versions of Ms. Pac-Man.

Atari 2600 version of Pac-Man
Atari 2600 version of Ms. Pac-Man
Atari 7800 version of Ms. Pac-Man
Intellivision version of Pac-Man
NES Tengen version (licensed release) of Pac-Man
Namco's 5 in 1 Plug n Play version of Pac-Man


Edit: I updated my list to also include Ms. Pac-Man.