Don't think, just do it.

Personally... I like playing as the smoker the best, nothing beats killing a survivor as his/her buddies look without being able to do anything, though Boomer comes in a close second.

It's really too bad that they don't have them anymore... I've probably sunken tens of hours of my childhood playing demos such as Roller Coaster Tycoon... Age of Empires and many others... and then buying the real games as soon as I could convince my parents to get them for me.

Or... he could just get Garry's Mod 9 for free and try it out, if he doesn't like it then end of story, but if he does then he'll buy it.

$10 for such an amazing mod is... a great deal though.

I highly recommend World of Goo... It's so good you have to play it for yourself :D

Any Total War games are totally worth it, Company of Heroes is one of the best RTSs I've ever played.

As for FPS, Battlefield 2 still has a very large amount of people who play it.

Yep, Orange Box is probably one of the best gaming deals in all gaming history...

I'm mainly a strategy gamer, so I recommend any Total War games, Company of Heroes and Civilization IV