Use the primary fire of your grenade launcher on an enemy turret to easily take it out quickly.
Ranger Zoom
Press L to zoom with the sniper rifle to zoom in. Press in the Right Analog Stick to increase the zoom.
Restore Vehicle Turbo
Exit a vehicle that has used up its turbo, then re enter it.
Telefragging
This can be done with any character as long as the person you are telefragging is on your own team. When you go up to revive someone, immediately after you revive them press Crouch to telefrag them. You will lose points.
The Avalon 2: Hidden area
In two player mode, when you are on the elevator someone can fall out by looking down right next to the computer. There is a space that you can use to crawl out, then the other player can push you out while you are trying to walk out that way. This may take a few attempts. When you are down there, do not talk to the repair man or else you will have to restart. Also, do not enter where the man walks out from or you will not get out.