What's the cheapest(per hour) game on your Steam account?

Terraria; 10€ 141h

Hmm... let's see. I got a Left 4 Dead bundle when it was on sale for $5.74, which would equal about $2.87 per game. Which would mean that Left 4 Dead 2 cost me about 0.0116 per hour of funtiems. :)

As for all of my games outside of Steam, Minecraft would be my best dollar per hour deal at around 0.0089. That's just an estimate, though, since Xfire wasn't able to track all of my offline time. And I have had several gameplay sessions when I wasn't even logged into it.

Titan Quest gold.

97 hours played after buying it for $5.

I play mostly single-player games, so I don't have many with a play time higher than that.