In a bit of a shocker, Gearbox Software's first person shooter Borderlands has taken the top stop in this week's list of the top 10 best selling PC games (based on revenue) on Steam. Left 4 Dead 2, Valve's own zombie shooter sequel, goes down to the number two position after spending the last few weeks in the number one slot.

BioWare's fantasy RPG Dragon Age Origins takes on the third spot this week (for the digital deluxe edition) as well as the fourth spot (for the regular edition). Despite tons of controversy surrounding the PC version in the past week, Modern Warfare 2 managed to debut on the list this week in the number five spot.

1. Borderlands - Gearbox Software/2K Games
2. Left 4 Dead 2 - Valve
3. Dragon Age Origins Digital Deluxe Edition - BioWare/EA
4. Dragon Age Origins - BioWare/EA
5. Modern Warfare 2 - Infinity Ward/Activision
6. ArmA II - Bohemia Interactive
7. Aion - NCsoft
8. Tropico 3 - Kalypso Media
9. Assassin's Creed - Ubisoft
10. Killing Floor - Tripwire Interactive