All Quiet on the Martian Front
A 15mm game set in a steampunk era, that puts the Martians Invading earth around WW 1. Tesla, Westinghouse, and others have fabricated great steam powered machines to battle the Martians. This game has a long history and has passed from many publishers. The genera and story line is what caught my attention. It scales very well from 2 players to a large multiplayer convention game.
Pulp Alley and Fist Full of Lead
Two of my favorites. Both games systems work for anything from Wild West to Space Opera and anything in between. Each game has its own play style, and have been very popular.