If you decide to go with the indie route, there are plenty of 80 MSP games that are worth adding to your library as others have stated.
If you like space games, try Abaddon along with Retro Overload & Abduction. As for zombies, Zombie Estate is really good if you don't mind the retro graphics along with ZP2K9 although it's more of a deathmatch kind of thing.