Awesome way to spend an afternoon in Vegas. This place is truly one of a kind -- tons of games, all in mint condition (or as close as possible), all obsessively maintained (no "Out of Order" signs or eating quarters). Old light & bell games, classics from every decade and the newest stuff too. My favorite is Funhouse. If you're having a low-key, cheap Vegas trip make sure to set an afternoon aside here. Break a 20 into quarters and by the time they're gone it's time for dinner. 20 bucks is gone in no time at the casino. Go have some fun away from the crappy generic music and maddening din of the casinos.
It can be tough to find the place, a move was planned when I was there last (2/09) but as far as I can tell it's still at Tropicana/Pecos. It's in a mini mall on the NW corner of the intersection.
(4/10 - apparently they have moved, these directions are for posterity's sake only.)