What game should I get my 12 year old brother for Christmas from steam?

Torchlight. Spiral Knights (it's free, but he might like it).

If he is interest in sport/fantasy games and doesn't give up directly if he isn't immediately good at something,you should maybe try Blood Bowl.

If youre not sure what games hes into or wants the most, its better to ask him about it. By just being subtle, you can find out without spoiling his surprise (if hes into surprises, if not just ask him whichever he wants}. I mean you guys can talk about gaming and make it seem casual hehe. Happy Holidays!

You don't need to buy him any games, just install planetside 2, gothamcity imposters, tribes ascend, black light retribution. You have all these amazing free to play games on steam with the quality of AAA titles you don't need to buy games unless you get a really good one.
If you still want to buy him a game I recommend : Bulletstorm, It is the perfect game for a 12 year old because it is about a 2 guys who lose their friends and go on an adventure to to discover what their friendship truly means and learn to leave the past behind.

Carmageddon.

Risen 1/2 or Binding of Isaac

Ace of Spades perhaps?

Buy Beyond Good & Evil for him. Awesome game with awesome characters! :)

Terraria. Or like someone said before - buy him a ball.

in all seriousness, some good games for him:
Sonic Generations
Darksiders
Bastion
Torchlight 2
Deponia
Spore Complete pack

borderlands 2

gta san andreas!

Amnesia.
/thread.

no one suggested rayman origins????

Universe Sandbox!

Batman Arkham Asylum. It's not that violent and has pretty good puzzles that he might find interesting.

Monkey Island 1 and 2. It isn't like Mount & Blade at all, but I don't think he played it and it's a very good classic game.

guild wars 2? ;p

We can't really know what he likes to play, but I would suggest games for every age like Psychonauts or Portal 1 and 2 ;)

Lego games :D

scribblenauts unlimited. because you can play it too. :D

Or buy him a book....

When I was 12 I got myself a copy of Crusader: No Remorse. Can't be found on Steam, but on GOG. Sure, it might be an ultraviolent game about you gunning down people (including civilians), setting them on fire, pealing the skin of their flesh with some exotic weapons, but it was good fun. Plus, it was not too hard on the easiest difficulty.

I also played Civ 2 and Command & Conquer: Red Alert back then, so how about Civ 5 and Command & Conquer 3? 12 is really an age where a kid will be able to play most games that are not "too" complex. I.e. giving him Victoria: An Empire Under the Sun or Pride of Nations might be a bad idea, but some basic RTSs or TBSs should be doable.

Modern Warfare 3. That's what every 12 year old plays.

A real suggestion would be Bastion, I think I would have loved playing the game when I was younger.

BFBC2 or SR3 :D

Scribblenauts