Grav Armor is the classic Dwarfstar game of future armored warfare. From the site:
GRAV ARMOR is a fast-moving game of future armored warfare for 2 players. It realistically simulates the high-speed, high casualty combat between streaking gravitic vehicles, surface-effects craft, supersonic fighters, orbital dropships and power-suited infantry. The modular map sections allow scenarios to be played on radically different types of planets (earthlike, molten, frozen or airless).
Hack and Sack New Jersey is a free hex style wargame about an alien invasion of New Jersey:
The alien Krylons invade the Garden State! Spaceships disgorge hordes of Cossacks and Roman-style legions; Jerseyite biker gangs and accountants fight back. 2 players.
Good Little Martian is a print-and-play card game for two players. The cooperative game has one player stranded on Mars, and the other on a rescue mission.
Pocket Imperium is a free print-and-play game in the 4X Genre (Expand, Explore, Exploit and Exterminate). It is designed for three players to finish in 45 minutes. The game features three spacefaring races.
Paranoia: Troubleshooters is a set of free rules for a card game based on the West End Games’ Paranoia RPG.