In the Raiders map, you could make a running jump into two oil tanks near the switch from which you can snipe enemies but cannot be hit by their return fire, even if they know you’re in the tank.
So I made an etpromapscript with some fake player clip brushes to keep players out.
http://images.bsdterritory.com/Mortis/raiders.script
Please report any new / additional bugs to me.
–Mortis
Here’s 2 pics of the exploit:

