Bitfighter is a game that feels a little like Asteroids on steroids. It's a multiplayer space-based combat and strategy game, featuring customized ships, multiple game modes, cool retro graphics, and smooth network play. It also includes a full featured level editor, Lua scriptable bots, and other cool features. It has a very active development team, so the game keeps improving.
Chicken Invaders 4 is a game in which you must resist an invasion of chickens from outer space. It features cooperative play with up to four players, 12 star systems to explore, 120 waves of invading chickens, a wide variety of weapons with upgradeable power levels, 30 unique bonuses, and 20 secret features.
War in Space is a shooting game. It's not a "Space Invaders" clone, but if you are familiar with games like that, you'll get the hang of War in Space pretty quickly. There are three girls ready to fly your spaceship for you, and each of them has their own quality and handicap. Pick one of them and you're ready to go. Shoot as many targets as you can and try to score big. It starts out very easy, but it will get harder and harder as the game progresses. See how far you can go. The game makes use of a patching system that allows you to 'modify' the game without destroying the original. An update is planned to make this compatible with the JCR5 project.