The Achievement aficionados over at Xbox360Achievments.org have uncovered the Xbox 360 Achievements for Left 4 Dead 2. The Achievements offer some insane challenges -- "Survive a campaign on Expert skill with Realism mode enabled" -- and, if accurate, also confirm the recently uncovered "Dead Center" and "Hard Rain" campaigns. The Achievements also detail some new features and confirm other rumored features, most notably a defibrillator which can be used to revive teammates. Also mentioned is an adrenaline power-up to boost speed, deployable ammo upgrades and ... a bile bomb. We really hope that last one does what we think it does.
Head over to X360A for the full list (warning: watch for spoilers ... and Tanks).
Update: A Valve representative has confirmed the veracity of the two posters as official, saying simply, "They're legit."