I'm big fan of Torchlight and original Mount and Blade.

I think I drop more hours on Torchlight than any other games I've ever played just because it's just so fun and entertaining for me. Also, piecing the gears is big challenge for me. It's nice to have user friendly interface so I'm able to enjoy it.

I got original Mount and Blade when it was on sale and it was blast. It's pure sandbox game, which is interesting because I have never play one before. I find it neat that I can do whatever I want to in that game without any restrictions.

Avencast. First game in years I've sat down and played start to finish without picking up another game.

It's basically like a deep hack-and-slash RPG, but with mage being the only 'class', so it's...uh...cast-and-chant?

Excellent storyline, too. Very very good.

Super Meat Boy.

Just no.

Sigh...

Mount and Blade games.
Lugaru.
Cave Story.
World of Goo.
Gish.
Penumbra series.
Gratuitous Space Battles.
Flotilla.
Bullet Candy.
Shadowgrounds series.
Audiosurf.
Braid.
Beat Hazard.
Darwinia.
DEFCON.
Multiwinia.
Uplink.
Time Gentlemen, Please! & Ben There, Dan That.
Misadventures of P.B. Winterbottom.

I could go on.

Limbo of the Lost.

World Of Goo, Audiosurf, Auditorium, Fractal.

I'm not a big indie fan but I love Cave Story.

Don't think I could pick just one. My 'finalists' would be :

AI War Fleet Command
Solium Infernum
Armageddon Empires
Mount & Blade Warband
Audiosurf
Beat Hazard
Take Command 2nd Manassas

Cortex Command, if I had to pick one out of the lot. Shame bout the community though.

-If he has a taste for horror, Amnesia/Penumbra.
-If he likes survival and sand box games, Minecraft.
-Platformers, Psychonauts/Super Meat Boy.
-Hack ‘n’ slash RPG, Torchlight.
-JRPG, with a strange mix between dungeon crawling and running a shop , Recettear: An item shop tale.

Well, they are what come to mind right now anyway.

Can't go wrong with any of these:

Avernum series
Deadly Rooms of Death
Defense Grid: The Awakening
Geneforge series
Mr. Robot
The Maw
Torchlight
Penumbra: Overture and Black Plague (Requiem isn't very good at all though)
VVVVVV

This is what kept me playing the original for over a year

Yes it´s a fantastic game. Most fun I have had with a game in years.

Really miss the old PC and 8/16-bit console game style.

Achron

This is a very innovative RTS using time travel as an integral part of the game play. It is kinda hard to wrap your mind around the first few times but it truly is one of the freshest RTS games ever.

http://www.achrongame.com/site/

Also they get bonus points for full Linux support.