For Rohan! Valve's Left 4 Dead team writes that Left 4 Dead 2 servers now run Team Chivalry and SeriouS Samurai's LOTR-inspired Survival mode map by default for players who subscribe to the map's Workshop entry. It's a celebratory move for a recent dedicated server fix and the ongoing beta for the Extended Mutation System, but c'mon—do you really need a reason to defend a massive stone fortress against waves of Saruman's mightiest undead?
I haven't run for my life in Left 4 Dead 2 in quite a while, but awaiting rescue from Gandalf while possibly yelling "AND MY CHAINSAW" into my microphone sounds like just the kind of fun to hook me back in.
