America's Army
If you play this game and find yourself overcome by an urge to run to the nearest recruitment center, do your best to resist it and sleep on it. Just give it a night to think it over. That's all we're saying.
Download it now.

Daikatana Deathmatch
Even though the game's designer posted a public link to this file himself, it's still assumed that you already own a copy of the regular game. But technically, you don't need it to run this online-only multiplayer shooter. Wait! Who is that looking over your shoulder? It's us, your conscience. Click responsibly.
Download it now.

F.E.A.R. Combat
You can find everything (minus the single player content) here. All the multiplayer maps, updates, and modes are included. Just head here for a free key after you start your download.
Download it now.

Above: FEAR Combat holds up pretty well and you shouldn't have a problem finding servers to play on

Gunz
The coolest thing about Gunz isn't its guns. It's the game's sword wielding classes who can deflect incoming fire with their blades. Rush in for a melee kill while your enemy is reloading. Download it now for some Matrix-like wall running and bullet dodging.
Download it now.

Narbacular Drop
The cake may be lie but Narbacular Drop isn't. This is the game that inspired our current obsession, Portal. Play as the "No Knees" princess and experience a slice of gaming history.
Download it now.

Penumbra
This horror shooter just might scare the pants off you. But seeing as how this game's free, we don't see why you should be frightened to give it a whirl.
Download it now.

Return to Castle Wolfenstein: Enemy Territory
Enemy Territory: Quake Wars is awesome. But you can check out developer Splash Damage's roots for some free fragging by clicking the link below.
Download it now.

Savage
This team based RTS/FPS hybrid has one person on each team who concentrates on building units and managing resources to produce more powerful units for their team to control. The creators have released the original for free to promote the upcoming sequel. It's a great idea and everyone should do it.
Download it now.

Soldier Front
All the usual suspects in terms of game modes are here in this military shooter. Deathmatch, various defend the control points and plant the bomb team based modes are here. And if you're serious, you can join or form a clan to conquer the world.
Download it now.

Toblo
Capture the flag with angels or demons in the fully destructible and surreal world of Toblo.
Download it now.

War Rock
With a name like this, how can it not rock? It can't. Or can it?
Download it now.