Blood (via Refreshed Supply)

God damn, it just might be one of the best first-person shooters ever made. Full of character, from its enemies to its arsenal to the levels you paint red. Yeah there's a lotta horror, sci-fi, and fantasy references (and even a few more besides), but they never overwhelm the actual experience of play, probably thanks to the non-existence of NPCs and the non-cinematic nature of the game. This is very much an old-school shooter, with slightly maze-y levels you can often traverse in multiple ways (the very first level is fantastic for this) while unlocking doors with special keys you pick up along the way. It's also brutally hard. Pretty much every enemy type is a threat, the hitscanners turn you into Swiss cheese, and the level designers hammer you with ambush after ambush. However, that makes it really rewarding to get into their headspace. When you can correctly answer the question “If I was a Blood level designer, where would I set up the enemies in this room?” you'll find the game opening out before your eyes.