1. If an Imp or weaponless Possessed's head and feet are just inside of the top and bottom of your combat shotgun's crosshair, firing will guarantee at least a stagger (orange/blue stagger).

2. Lost Souls can be thrown. If you have Beserk, you can punch the side of a Lost Soul to "redirect" it into other enemies. This doesn't always work, however.

3. Possessed Soldiers can be killed with two shotgun headshots.

4. Headshots do increase damage, as well as the rear side of pinkies, the cacodemon's eye, and mancubi stomachs.

5. Feet glory kills where you kick an enemy into the air and punch their face in (works on players as well) are usually the fastest.

6. Barrels have a chance to stagger anything up to a Hell Knight with full health.

7. Running directly forward is slightly faster than strafing, moving diagonally, or moving slightly off center with a controller.

8. Cacodemons & Hell Knights can be killed with a single Siege Mode blast. (Credit to "UnitedDucks" & "ɮƦعѦҚ ϟ†Ʀ¡ҚεƦ")

9. Two point blank Super Shotgun blast will stagger Revenants. (Credit to "briglicon")

10. Two precision Gauss Cannon shots will kill Mancubi if they are both headshots (Credit to "briglicon")

11. Hell Knights and Pinkies both primarily use charge attacks which can be sidestepped.

12. The most effective buffs with a quad damage are the micro missiles and super shotgun which devastate when used accurately. (Credit to "Magné")

13. A single charged guass rifle will kill cacodemons, hellknights and anything weaker in a single shot. (Credit to "LordMix")

14. Charged Shotgun, meet Barrel. (Credit to "SAS: Officer of the Server)

15. A charged gauss shot is the most damaging attack in the game second to only the BFG. It can kill Barons with two headshots. (Credit to "Accelerator")

16. The trick to defeating pinkies is waiting until they charge you, then sidestep (or double jump if you have the boots) over them or stun them, and fire super shotgun or explosive shotgun shells into their rear. (Credit to "Masterbio" & "Lord Casselstone")

17. All unarmed Possessed and Unwilling can be staggered with a single melee attack. This helps in conserving munitions, and also turns them into walking Health replenishers. On Nightmare/Ultra Nightmare they all must at least be shot twice with pistol headshots before this works. (Credit to "BlackBlood15532")

18. Soldiers armed with shields are best fought by getting around them so they can't get a shot on you (you move faster). Watch that you keep a moderate distance however, as their melee attacks can be fairly damaging.

18a. Do not try to beat a shield by jumping over him if you can help it. Especially on NM or UN, his shotgun rapid fire will kill you instantly with full health and armor. Use your grenades and your shotgun grenade attachment to blast him and make him raise his sheild up. Do not try to kill these guys fast because you'll end up choking. (Credit to "Poundcake Jr.☭")

19: When fighting the Cyberdemon, save your BFG ammunition until the second phase, then start using it whenever he spawns that hallway of spikes around you. Then go in on him with a charged Guass shot. (Credit to "Admiral Crackbar")

666. The music is awesome.