The new weekly list of top 10 best selling games on Valve's Steam service has their co-op shooter Left 4 Dead in the top position again after Team Fortress 2 took the top spot last week. We are going to take a wild guess and guess that's because of the Left 4 Dead 2 announcement at E3 this past week.

The other interesting thing about the list is the continued success of Killing Floor. Tripwire Interactive's co-op shooter is number two on the list and has remained in the top 5 since its release a month ago. Perhaps Tripwire will also get a sequel for the game out the door quickly.