A few years ago, a guy by the name of SgtMarkIV decided that Doom wasn't violent enough. So he made a mod for it.The end result was Brutal Doom, a mod that takes the original game (or Doom II, or pretty much any IWAD you throw at it) and pumps new life into the aging classic. Taking cues from the infamous Doomcomic book, Brutal Doom allows Doomguy to perform all manner of new tricks on the forces of Hell, and for them to respond in kind. The mod is continually updated over the years.Can be download online, but be forewarned — to say that this mod is gory is an understatement. You will literally be painting walls red.Note: As the mod relies on the data from whatever IWAD you use with it, all tropes listed on the Doom page also apply here.
Brutal Doom provides examples of the following tropes:
The mod replaces the Partial Invisibility power-up with a chained fellow marine that can be freed and then offers more firepower. Those marines have the same artificial intelligence than the standard monsters, so they can (and probably will, especially when fighting in a doorway and/or with explosive weapons) hurt the player while targeting enemies. Also, they have no understanding of wall/ceiling traps and will cheerfully walk into them while randomly sprinting around the level.
The allied marines A.I. has actually been greatly fixed since version 0.19.
Revenants can be blown in half and their upper half can be just as capable of hurling rockets at you. Meanwhile their legs will amusingly waddle around aimlessly before falling over.
Awesome, but Impractical: the Mancubus' flame cannon. It deals a decent amount of damage, but basic enemies will be set on fire by it, at which point they'll proceed to run around aflame for a long time, bumping into you and dealing flame collision damage.
The Berserk packs get an upgrade from their Awesome, but Impractical status in the vanilla game. Grabbing one enables you to perform fatalities with the killing blow (which you're invincible for) allowing you to aim yourself at the next enemy, strike as soon as its over and quickly transition into the next kill. You even get some health back for each fatality you perform, and you can also grab Lost Souls out of the air and hurl them as makeshift explosives, as well as pick up and throw exploding barrels.
The assault rifle, which replaces the pistol. It's the most accurate weapon in the mod, fires much faster than the pistol and has a secondary fire mode that allows you to aim with the sights and snipe from afar.
Back Stab: Punching an inactive and unaware zombie or imp from behind triggers a short third-person animation showing the Doomguy killing said enemy with a quick Neck Snap.
Badass Boast: There's a button to pull one off. Usually uses a line from the comic. Unfortunately, this was Dummied Out in version 0.19.
Blood Knight: If he wasn't one already, this mod makes Doomguy into this. He will sometimes laugh triumphantly after performing a fatality on an enemy.
Cluster F-Bomb: If you play Brutal Doom online, chances are at some point you'll all start invoking this trope.
Covers Always Lie: This mod averts the vanilla game's oversight by replacing the pistol with an assault rifle.
Difficult but Awesome: Groin attacks (see below) are tricky to pull off against the opponents you can perform them on, but they stun-lock for a good few seconds, allowing for a coup-de grace with a close range weapon.
Dummied Out: v0.19 still has the hidden MP40; the player just has to use the console to get it, since the only enemy that dropped it actually was removed.
Exploding Barrels: Aside from standard barrel behaviour from the original Doom, non-flaming barrels can be picked up once you have a Berserk pack and thrown for a massive boom. Walking right into barrels allows to move them. Flaming ones can be kicked and rolled on the floor, leaving behind a trail of flames.
Finishing Move: Melee attacks under the effect of a Berserk pack or Demon Strength Rune will trigger this and melee attacks of most monsters will do so as well if they kill you (or each other) with them.
Flipping the Bird: You can flip off (and insult) whatever is stands in your way with a simple push of a button, and it's conveniently mapped to the F key by default no less. It is actually a useful way to wake up unaware enemies without wasting ammunitions.
Follow the Leader: There are a fair few variations of Brutal Doom that have been created by other Doom modders, and that's not even counting the "Mutator" side-mods that have been released.
Grievous Harm with a Body: With a Berserk pack, you can grab Lost Souls and chuck them at whatever you please. Hell Nobles (Knights and Barons) also have the ability to chuck zombies at you, and Revenants can do the same with imps (after slamming them around a bit). You yourself can use zombies as human shields if you grab one you've previously wounded, and launch them at your enemy when you're done.
Groin Attack: Can be done on Chainguners and all Hell Nobles.
Half the Man He Used to Be: One of Doomguy's finishing moves after getting a berserk pack involves ripping and tearing an enemy half from the torso.
Heart Container: Health and armor bonuses can still boost your stats beyond 100 as they normally would, however, they can go beyond vanilla Doom's cap of 200.
High-Pressure Blood: Happens sometimes when zombies and imps have their heads blown into bits - they'll stand in place while blood spurts out from their neck for a few seconds before their bodies finally drop.
Invulnerable Attack: You are completely invincible when performing fatalities. This means you can be pelted by projectiles from five different directions and not feel a single thing until you finish stabbing that Pain Elemental with its own horn. Unfortunately, this also applies to enemies.
Man on Fire: Happens to the zombies, imps, pinky demons and the marine himself if they are killed by fire. They deal collision damage, so it's advisable not to get too close with them.
The Many Deaths of You: Just your enemies can be killed in brutal ways, the same applies to you. Demons can bite your head off, Former Commandos can blow a hole into your torso, your body melts if you die in a vat of acid, and then some.
Nerf: Prior to version 0.19, the default maximum you could carry for bullets was 300 (and 600 with a backpack). In version 0.19, those stats have been brought back to their unmodded values of 200 and 400.
The greatly heightened threat of the enemies can play hell with the intended difficulty level of certain third-party maps. Brutal is intended to turn the original Doom levels from somewhat hard to fairly hard, but if a map pack is tuned to be very hard in the original game it can become almost impossible to beat it in Brutal — and occasionally downright so; see Unwinnable example below.
Non-Indicative Difficulty: The theoretically easiest difficulty level ("Power Fantasy") gives you Ultra-Violence and Nightmare's enemy frequency, but they only deal 30% damage, allowing you to mow down hordes of monsters with impunity.
Overdrawn at the Blood Bank: With some extensive usage of all the weapons you can carry, you will be able to paint the walls a very thick coat of red, and most of the finishers delivered by Doomguy and the monsters release generous amounts of the red stuff. Fire a BFG in a room full of weak enemies, making sure you're seeing all of them for the invisible tracers to hit. Holy crap.
Precision F-Strike / Flipping the Bird: At the push of a button. "FUCK YOURSELF!" One side mod makes the finger taunt a literal strike, making anything you flip at explode into gore.
Rated M for Manly: It's badder, bloodier, and filled to the brim with heavy metal mayhem.
Red Eyes, Take Warning: The spectres' appearance has been altered. In the unmodded games, they look like a highly visible pinky-shaped smoke or shadow. In the mod they are invisible until they attack, except for a pair of glowing red eyes and the nearly totally transparent shape of their body.
Take That: Prior to version 0.19, the Commander Keens were reskinned with Justin Bieber's face. Since then, the reskin was removed.
Those Wacky Nazis: Again prior to version 0.19, in both Doom IIWolfenstein 3D-themed secret levels, the blue-dressed and comedically accented SS enemies were replaced with more realistic troopers wearing grey dark uniforms and shouting actual German phrases (taken from Call of Duty 2). They also carried MP40s that could be picked up and used by the Doomguy.
The "Cruelty Bonus" (a health or armor boost) is granted when you kill enemies in a particularly creative fashion — usually those whom you've just dismembered or set on fire.
It can take some effort to master killing monsters with fatalities — if you go about it the wrong way, punching an enemy to death is likely to rob you of more health than the fatality gives you back, to say nothing of armor. But watching the bad guys being torn to bloody shreds by the Doomguy makes it so worth it.
Video Game Flamethrowers Suck: Version 0.19 changes the plasma rifle's secondary fire into a flamethrower and averts this trope rather strongly - the flames are very effective at leaving charred remains where once stood enemies, the only downside being they eat through your ammo in no time.
Universal Ammunition: As the pistol is replaced by an assault rifle, its common ammunition shared with the chaingun now makes sense. On the other hand, versions prior to 0.19 also added an MP40, which in-game fires the same ammunition used by the M16-shaped assault rifle; one of the points that identifies a submachine gun (which the MP40 is, "MP" being short for "machine pistol" in German) as such is that it is a pistol-caliber automatic weapon.
Unusable Enemy Equipment: Averted. With the right tool, you can acquire the Mancubus and Revenant's weapons. Explode them with the rocket launcher, kill them with the chainsaw, or chainsaw the corpse. The SS replacements in versions prior to 0.19 likewise dropped their unique guns on death.
Unwinnable: The mod is made for the original Doom levels, and it's optimized for a small number of other mods as well. But every map-replacement mod ever made for Doom can be played with Brutal as well, including some that make assumptions about gameplay that are no longer true with Brutal Doom. For instance, a map that spawns a Cyberdemon in a relatively small enclosed room and relies on the player's reflexes to dodge its rockets can easily become unwinnable because the Brutal Cyberdemon fires much faster and its rockets have massively increased area damage, enough that nowhere in the room can the player not sustain enormous damage and die from the Cyberdemon's first or second attack.