I found this wordpress blog post to be both informative and interesting.  Did you know that once you set a Tank on fire, it is going to die X seconds later, no matter if you shoot it or not?  Or that if it jumps in the water the fire goes out, but it will still die X seconds later?

Useful stuff.  I’m going to have to try some of this out.

http://espion4ge.wordpress.com/2008/12/30/left-4-dead-tips-for-surviving-expert-difficulty/