Barrel Inertia
	When barrels are shot or are within the blast radius of an explosive, they are damaged, which makes them move, and if damaged enough, explode. If you come across a row of barrels, you can use this to your advantage. In the picture at left, the right barrel was shot, moving the left barrel away and exploding it shortly after. You can use this trick to take out many enemies with one shot.

Hall-Dodging
	When trapped in a thin hallway with a fireball-throwing enemy, avoiding its shots probably seems hopeless. However, you can easily throw off an enemy's aim by staying on one side of the hall, waiting for it to fire, then quickly moving to the other side and backing up.

Tricking Revenants
	The Revenant is a terrible enemy; it can launch guided missiles and punch. Fortunately, you can use one to avoid the other. When fighting a Revenant, run up to it briefly so it winds up for a punch, and quickly back up. While the Revenant is still punching nothing, shoot it. This trick stalls your enemy.

Telefragging, In a Way
	It's never a bad idea to hit the fire key just after running into a teleport for the first time. There could could be a couple of Imps or Shotgun Guys facing the teleport, and the sound of the teleport and the green blur can make them unnoticeable at first, giving them a chance to shoot you.