What are people's recommendation for their favourite FPS single player campaigns that you still enjoy playing a couple of levels once in awhile? No multiplayer suggestions.
My all time one is Medal Of Honor 2010 reboot. I don't play through it every time but I have a couple of favourite levels.
The Bungie era of Halo (Combat Evolved through Reach). You can never go wrong with those games, and the soundtrack alone will get you pumped to play through humanity's last stand.