Xenogeddon is a free open-source FPS where you walk around an abandoned ship avoid the enemies that might or might not lay in wait. Your mission is to activate the self-destruct and then escape. Please note that at the moment it is in beta.
Programmed by Stephen Smith (stephen.carlylesmith AT googlemail.com). It’s loosely based on Space Hulk by Games Workshop.
For windows or Linux.
Looks Quake-ish.