If you want a good sci-fi shooter that isn't Mass Effect and you aren't afraid of a little age, check out Star Wars: Dark Forces and the sequels. They're all on Steam. Caution though, they ARE a little old!
I have a G5 from 2007. She's still in active duty [currently being loaned to my housemate] and she still works just as well as when she came out of the box. Doubt I'll ever find a mouse as good as she's been to me.