Realistic zombie mod of ARMA 2. Been playing the hell out of this. It's pretty intense, the goal isn't to win, just survive.
So after seeing this threads months ago, I've been really interested in ARMA 2 and mods like these. Day Z never quite did it for me but this new mod, called Wasteland, has been really cool to watch thus far. It's basically a more flexible, resource-based team vs. team game, sans zombies. In all honesty, most player vs. player Day Z games I've watched treated the zombie like nuisances with the main focus being finding loot and killing other hostile players. In Wastelands, there are only players and it has more of an end-of-the-world/mad max vibe. you can chose between 3 factions (BLUEfor, OPfor, and independent). You can't kill your own team, and the independents can choose to align/fight with anyone. There's also random objectives to complete and stores to buy equipment.
The videos below are from the same guy. He kind of a talks down to people (read arrogant), but has great ARMA/DAY-Z/Wasteland videos. His crew has a realism unit, and they make videos as a whole platoon on ARMA conducting simulated military operations against the AI. His channel is worth checking out.