Pretty good RTS game for the price. In fact the main reason I wouldn't call it glorious is due to the free to play Company of Heroes Online. Though with this you get some fairly entertaining campaigns.

Fun multiplayer game. Various game modes and classes (Planes), customizable perks and weapons, overall a decent time. Game's also free for the weekend so give it a shot, well worth looking at.

A good game, but the only reason this gets a bad rating is because the superior Warband is available for $10. The only reason you might prefer the original over the expansion is for mods, and even then many of them are being ported to Warband.

Great open world medieval sandbox, you can work for kingdoms or start your own, build up armies, raid people, kill bandits, and level up. Warband also has large scale multiplayer if you want to run around and sword other players. Perhaps most importantly achievements were just added such as HOLY DIVER. Highly recommended.

Multiplayer indie robot battle. I know absolutely nothing about it but it's $2 and that's cheap enough to be worth looking at a multiplayer indie game.
UPDATE: Pretty god damn cool game. Servers are (currently) very well populated and the game has some great simple gameplay. At $2 it's well worth checking out, even if there's a chance it'll lose players quickly. Not something you're likely to play for hours and hours but it's excellent for short bursts.

The two best Stalker games at a good price, a lovely deal. Open world shooters with mutants, anomalies, and eastern europeans playing guitars. Slow paced and with semi-realistic damage and gunplay, they aren't for everyone but at this price if you're at all interested it's a good place to start. Both games also aren't Starcraft 2.

Supposedly a decent action RPG for at least one play through. Haven't tried it yet myself but I've heard fairly decent things and at least it isn't Starcraft 2.

Borderlands once again going on sale. Fairly decent action RPG FPS hybrid, you go around shooting the stuffing out of baddies and treasure falls out. Every copy of Borderlands sold increases Complex's risk of heart attack and stroke, so buy with gusto.

Dr. Ned is decent but a separate area entirely disconnected from the rest of the game, you can pretty easily avoid picking this DLC up. But if you want more baddies to shoot, particularly zombies, then here you go.

Mad Moxxie is a grindy as hell arena. Probably fun enough if you've got buddies with you but pretty terrible solo.

Of the DLC, I really recommend Knoxx which raises the level cap, adds more guns, and vaguely follows the story of the original game. Also the most difficult.

I like simple arcade style games where you rack up points as much as the next guy. Hell, probably even more than the next guy, but Foreign Legion just isn't terribly good. Poor enemy variety, poor map variety, fairly poor weapon variety. It's not entirely worthless, but $2.50 is about the upper limit of what you should pay. Only get it if you want really simple mindless man shooting for points.

I haven't played this, but I'm going to advise caution. Multiplayer focused indie games are risky beasts, and it would be a bummer to spend $8.50 and find yourself all alone. Day in, day out, sitting at your computer, loading up Steam, staring at the empty servers. Your life used to be better than this. You used to go outside. You used to have friends. No more. Gabe Newell's laughter playing again and again in your head as you wait for death to take you away from this living hell.
Or maybe people play it and it's a fun game. Who knows?

Quake 1, both Quake 1 mission packs, Quake 2, both Quake 2 mission packs, Quake 3, Quake 3 Team Arena. A lovely package of oldschool shooting. A very unfortunate downside is that Quake 1 and Quake 2 don't have music on Steam.

Not a fantastic price, but quite good for a fairly decent game with a bunch of fairly decent DLC. Might not be a particularly good RPG, might not be a particularly good Fallout game, and might not be a particularly good shooter, but as a whole Fallout 3 is a pretty good time. A recommended purchase for the Swedes among us since it teaches you that democracy is truth, communism is death.

Buy this so you don't have to play Doom in a browser without music using the original WSAD like a horrible monster. You can either play Doom 1 and 2 in their original form from Steam, or download one of the fan made engines such as http://doomlegacy.sourceforge.net/ if you can't bear the low resolution.
Doom 3 isn't up to snuff with the others but is a decent enough game.

I know nothing about the game beyond it being a sidescrolling primarily multiplayer shooter along the lines of Soldat. However this weekend (Starting now) it's free to play, so download the 400 megs if you're interested and give it a try. 260 Steam achievements included if you want to achieve. ARE YOU THE BOOSTINGEST TROOPER?
UPDATE: Holy Christ this game is terrible. Do not buy for $5. Only try the free weekend at your own peril. Just tried it myself and it hurt.