Counter Strike Global Offensive
Today's update includes two maps (de_vertigo and ar_monastery), a wide range of fixes, and an overhaul of the matchmaking for the Classic Competitive mode.
If you are stealthy enough, you can stab your knife in the enemy's back. Play against real players for best experience.
CS: GO features new maps, characters, and weapons and delivers updated versions of the classic CS content (de_dust, etc.).