I'm on a 20 dollar budget and want to buy a new game from steam, any suggestion? It can be RPG, FPS, or RTS. I don't care if the game doesn't have dated graphics or not and I certainly don't care if the game is a little buggy. It must have multiplayer with people still playing it. Half Life looks nice but I'd rather wait until I have a higher budget so I can buy all those games in a bundle.
List of games I already have:
CS:S
TF2
GMOD
BF2 The Complete Collection