Left 4 Dead Tank

The Tank is the single most powerful character in Left 4 Dead, but takes some time to learn how to control effectively. I've covered the basic controls previously [link], but there are some other intricacies as well.

Control of the Tank can be passed to another Infected player. It is rumored that using LT to throw at another Infected will transfer control to that player. I have definitely seen control of the Tank passed off after the first player timed out and lost control.

If the human players lose control of the Tank entirely (both time out, or AI doesn't transfer to a second player), the Tank will be taken over by the AI. If there are no humans around, the Tank has been known to stay where he was last controlled until disturbed by humans. This has some interesting consequences. The AI Tank will then effectively just wait in hiding as a nasty surprise to the Survivors, because the typical Tank warnings (scary music and shaky screen) will not appear before the attack.