We use this for enabling the sentries during humilitation:
http://forums.alliedmods.net/showthread.php?p=879948
We have it set so that there is a 50% chance of them being active and a 50% chance of them betraying their original team. It keeps people on their toes at the end of round.
The flame thrower has never been able to damage teammates, if it could be done be an extension, then I'd be interested in running it too (plea to those that can code extensions).