Tank Duel is a set of free wargames rules for WWII games where each player commands a single tank.
Hell On Wheels WWII Tank Tactics
Hell On Wheels is a game of tank warfare in France in 1944. Players command a platoon of tanks.
Reanimation Zombie Survival Card Game
Reanimation is very highly rated at Board Game Geek. And it is free.
Dice of the Living Dead
Dice of The Living Dead is a free print-and-play zombie survival horror game.
Western In My Pocket Free Print and Play Game
Western In My Pocket is a free print and play tile game. From the BGG description:
Players lay tiles beginning at the Sheriff’s Office, and must find dynamite at the Survey Camp and get to the mine and blow it up before noon. While you’re doing this, there are bandits around that will try and stop you. Western in my Pocket features a modular board, so no 2 games are ever the same.