I'm surprised no one mentioned POSTAL, the 1st one. May not be a FPS but it allows you to play as a psycho killer in various situations, just like a reversed horror game where you make the (thousands of) victims. Haha wtf Japan... correct me if I'm wrong but isn't there a game from Enix from their 1st contest that involves protecting a schoolgirl from being killed in traps and assassination attempts, and she strips if you protect her? Based on a real schoolgirl relative of the programmer complete with an accompanying tape with her real voice(!)?
^ive had Undying on my list for years, how does it hold up? thinking i might try that one after I finally get through System Shock 2.