Transcendence is a rogue-like space scrolling shooter with story elements. You can make mods if you know XML.
(http://i54.tinypic.com/2dqop3b.png) And with a mod: (http://i54.tinypic.com/o8i52h.png)
Website: http://www.neurohack.com/transcendence/ (http://www.neurohack.com/transcendence/)
Mods and more: http://xelerus.de (http://xelerus.de)
How to use mods: If the Trans101 folder doesn't have the "Extensions" folder in it, make it. Extract or unzip the files to that extensions folder. WARNING: some have bugs and may not work.