Something strange may happen today when you log into Team Fortress 2…

Quietly, and without fanfare, the guys at Valve started a promotion bundled with pre-orders of Left 4 Dead 2—you will receive a special hat if you own Team Fortress 2.  The promotion, attached to both Xbox 360 and PC, was announced yesterday.

The other interesting thing mentioned in this announcement is a subtle allusion to a tenth class in TF2. First hinted at in Left 4 Dead, it has slowly faded into the background as time has passed.

It is also worth mentioning that this is the first official cross-IP content in any Valve game. Valve’s tactics of subtlety and humor continue as Left 4 Dead 2 launch day approaches.