While I'll never be fully comfortable playing games set in the contemporary forever-war continually in the background of modern life, I must admit that Insurgency is a solid little shooter. Originally based on the Source mod of the same name, it offers realistic class-based tactical manshootery both competitive and co-op. For the next two days, it's free to grab in order to promote its upcoming sequel, Insurgency: Sandstorm, due out next month. Grab it now on Steam, keep it forever.
While gritty realism and modern-day firearms are of limited appeal to me, I've had some good times playing Insurgency's co-op modes, which are also a great place for new players to start. Insurgency never quite reaches Arma's level of infantry fidelity, but it's an uncompromising experience where caution and team cohesion are frequently more important than a fast trigger finger. It's also consistently well populated, with Steamcharts estimating that you'll find a good 2000-2500 players on at any given moment, making finding a populated server a cakewalk.
The game offers a good range of playmodes, including several larger-scale modes with respawns and reinforcements. For those preferring a more Counter-Strike style of play, there's a few 'tactical' variants where you're got either no respawns, or very limited lives. Elimination in particular is almost identical in structure to Counter-Strike's Demolition mode. It's a big game, too. 16 maps, plus eight more night-time variants. They're a nicely varied bunch, too, with some larger outdoors maps, tight urban warrens and some heavily shadowed interiors to get sniped at from.
Insurgency is free for the next 48 hours on Steam. Click now, keep it forever. It should be available until 6pm BST, on Wednesday, August 15th. The sequel, Insurgency: Sandstorm is due out on September 18th.