Team Fortress 2, but we still get excited about the game's hilarious updates. In its most recent patch, TF2 received the new "Highlander" mode, in which teams are composed of nine players -- but each team can only have one of each class. In other words, "There can be only one (Spy, Sniper, Heavy, etc.)." This not only sounds like an interesting new mode, but it also gives us occasion to link to the intro for the Highlander television series, which scientists recently concluded is the coolest intro sequence in the history of mankind.
We're also guessing the ultra-Scottish Demoman class gets some sort of intangible benefits while playing in this mode, but that's just pure speculation.