This Reaper 3-D, an open-source spaceship combat game seems to be underrated. It is of the same style as Terminal Velocity, but with better goodies such as improved 3-D ground objects (instead of flat, sprite-based ones like in TV). The OpenGL-based graphics is amazing, though it lacks the fast-paced background music which – in TV – pumps the adrenalin faster and faster. And granted, it has not been updated anymore since few years ago although the last release was still fun enough to play.
Give it a try!