Any good fps games? (Besides the popular AAA titles)

Garry's Mod, Payday 2, 7 Days to Die, and DOD:S are some pretty good ones. Garry's Mod has p much anything you could want(within boundaries of source engine and your computer), Payday 2 has a good offline/online campaign that can be played with/without friends, 7D2D is still beta(since the beginning of time) but fun as hell with friends(I've played for >3 hours in one sitting thinking it was 1 hour), and DOD:S is an oldie but still has an active community.