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.
Naev is a 2D space trading and combat game, in a similar vein as Escape Velocity. Naev is played from a top-down perspective, featuring fast-paced combat, many ships, a large variety of equipment, and a large galaxy to explore. The game is highly open-ended, letting you proceed at your own pace.