I wish I could put this one down as best but I never got my grubby little hands on it. So I'm throwing my hat in the ring for Sunset Riders. Fuck yeah. I was always the green Mexican guy with the shotgun. Because shotgun.
This was a fun little FPS built on the Dark Forces engine, complete with a painfully-cribbed-from-Morricone score. (I mean BLATANT cribbing - it was like they just cut up a "best of Morricone" album, threw it in a blender, and strung together whatever came out.)