Red Faction 1, in 2001 on PC, by a long shot. Tunneling through maps, creating your own maps, it was the best out there. Battlefield 2 is the classic of modern military shooters, and that thing had the best mods, Project Reality Mod in particular.

Forget them both and get Rainbow Six Vegas 2. So many modes, multiple respawns (amount can be set), rappelling, loads of maps. Can do multiplayer pvp battles, can do online co-op terrorist hunts with up to 4 people, and can do the campaign co-operatively online, as well. AND DON'T FORGET ABOUT 2-PLAYER SPLIT-SCREEN. Hello. NO games have that anymore.

Get Rainbow Six Vegas 2. It's extremely tactical. It's an FPS, but at the same time, you can go to cover like Gears of War. You won't regret it. I've been playing it for weeks and it's not getting old at all. You can create your own character, different appearances, equipment, etc, choose weapon combos and community is great. I'm not lying. And I've played EVERYTHING. Warhawk is a joke, and SOCOM isn't a fun tactical shooter, like Rainbow Six Vegas 2. Plus, R6V2 supports two offline modes, terrorist hunt and campaign.

Buy what you want, but I'm telling you the truth.