I loved the idea in that thread. I figured there must be a complete list for everyone comment and improve upon, so I decided to make "splatters" for every combination. Since this is rather long, a new thread would be easier on the eyes.
I didn't include the Spear because I never got it, and merged all shotguns into one category. And I made all unarmed splatters on the basis that it's performed on berserk. I don't think anyone will be punching a baron unberserked anytime soon. Here thet are:
Unarmed
Former Human/Sergeant/Captain/Commando: You grab the former human's head and snap it before it can react.
Imp: You feel the imp's ribcage cave in as you punch.
Demon: As it is about to bite your head off, you catch the demon's jaws. It vainly tries to shut its mouth as you rip its lower jaw off.
Lost Soul: You catch the lost soul with both hands and pop it like a pimple.
Cacodemon: You plunge your hand into the cacodemon's huge eye. As it opens its mouth to hiss in agony, you catch its tongue with your other hand and rip it off.
Pain Elemental: You catch the flimsy arm of the pain elemental and rip it off with ease. It only has time to moan once before you plunge its own limb into its big eye.
Hell Knight/Baron: You grab the hell knight/baron's horns with both hands and heatbutt the beast, much to the surprise of it. Then you keep heatbutting it until its horns come loose.
Arachnotron: You stomp on the arachnotron's gray matter and squash as if it was a cigarette butt.
Arch Vile: You catch the arch vile in a headlock and keep pressing until you hear its neck crack.
Cyberdemon: You dart between the massive demon's legs and perform a mighty uppercut. As you feel its family jewels cracking, the towering monstrosity whimpers like a beaten puppy.
Knife
Former Human/Sergeant/Captain/Commando: You hammer your knife into the former human's skull.
Imp: You slash at the imp's neck and are rewarded with a geyser of blood.
Demon: You stab the demon's both eyes before it can blink.
Lost Soul: You swat the lost soul with your blade, as if it's a mosquito. The results are strikingly similar.
Cacodemon: You lodge your blade into the lower portion of cacodemon's eye and manage to tear it out in one piece.
Pain Elemental: You ram your knife into the pain elemental's forehead.
Hell Knight/Baron: You stab the hell knight/baron first in the snout, then on the stomach. You then grab his injured snout, force it up and slice its neck.
Arachnotron: You skillfully cut the arachnotron's face off as if peeling an apple.
Arch Vile: You plunge your blade into the arch vile's groin when it raises its arms. It lets out a shriek but is abruptly stopped when you ram your knife in from below its lower jaw.
Cyberdemon: You jump and grab the towering cyberdemon's rocket launcher. As it tries to shake you off you reach out, stab both of its eyes then slice its neck as it roars in a blind fury.
Chainsaw
Former Human/Sergeant/Captain/Commando: You rip the former human in half from its waist.
Imp: You decapitate the imp with a swing of your chainsaw.
Demon: You saw right through the demon.
Lost Soul: You slice the lost soul in half, as if it was a melon.
Cacodemon: You see some sort of orifice at the back of the cacodemon, and plunge your chainsaw in. It is almost cut in half as it slides from your chainsaw to the ground.
Pain Elemental: You cut the pain elemental into two hemispheres of bloody flesh. The lower half immediately falls, but the upper half manages to glare at you for a moment before falling.
Hell Knight/Baron: You start from bottom between the hell knight/baron's legs, and work your way to the top from there with your chainsaw. You twist the chainsaw at its neck, its two halves fall apart and the head flies away.
Arachnotron: The arachnotron's fleshy bits are mincemeat when your work is done.
Arch Vile: The first swing of your chainsaw lops off the forearms of the arch vile and the second swing amputates both of its legs as it screams in agony.
Cyberdemon: You leap up and chop off the cyberdemon's rocket launcher with a swing of your chainsaw. It topples, and you slice its head in half.
Pistol
Former Human/Sergeant/Captain/Commando: A single bullet through its eye puts the former human down for good.
Imp: You shoot the imp on the forehead. It stands a moment, squinting its eyes to see its forehead, fails and falls.
Demon: When you shoot the charging demon, it simply falls and rolls a little forward.
Lost Soul: The bullet has a similar effect on the lost soul it would have on a molotov cocktail in mid air.
Cacodemon: The cacodemon dies.
Pain Elemental: You shoot into the pain elemental's mouth. A newly spawned lost soul is hit before it can be released, exploding the inside the elemental's mouth. The pain elemental dies as the explosion tears it apart from inside out.
Hell Knight/Baron: A bullet to the groin drops the hell knight/baron just as it would drop anything.
Arachnotron: You hit some sensitive spot on the arachnotron's mechanical body, causing it to go haywire. The fleshy bits fall to the ground as its body rears up, then the legs violently stampede about until it tramples its own squishy gray matter.
Arch Vile: The arch vile can't figure out how a pesky bullet managed to kill it.
Cyberdemon: You face the towering cyberdemon. You eye each other cautiously as tension builds up. Suddenly the cyberdemon fires its rocket launcher, faster than you can react! But it's empty! You smile to yourself and shoot him three times before it falls.
All shotguns
Former Human/Sergeant/Captain/Commando: The former human's shoulder, arm and a portion of the ribcage is blown away.
Imp: The imp's head explodes into a mass of bloody bits.
Demon: The demon's face is replaced by a cavity spraying blood and bits of flesh.
Lost Soul: The lost soul is literally ripped apart.
Cacodemon: You fire into the cacodemon's mouth as it's about to shoot a plasma ball. The shell blows through the back of its mouth and you can briefly see through the new hole before the monster falls.
Pain Elemental: The pain elemental's eye explodes into some opaque fluid with occasional pink bits in it.
Hell Knight/Baron: The hell knight/baron is knocked onto its back and doesn't get up.
Arachnotron: You blow the arachnotron's brains out, which constitues almost all of it.
Arch Vile: The arch vile is hit squarely on the waist with the shells, seperating its torso and hips.
Cyberdemon: You hit the cyberdemon's rocket launcher with the shotgun. It explodes, and gives you the chance to shoot your load into the screaming demon's mouth.
Chaingun:
Former Human/Sergeant/Captain/Commando: The former human is filled with lead.
Imp: The imp flies away as you keep pouring lead into its already airborne body.
Demon: The onslaught of bullets bring the advance of the demon to a permenant halt.
Lost Soul: The lost soul reacts to a volley of bullets much like a bottle of molotov cocktail would.
Cacodemon: The cacodemon can't float anymore, what with the amount of lead in its body and all.
Pain Elemental: The pain elemental dies of acute lead poisoning.
Hell Knight/Baron: The hell knight/baron looks like a sponge immersed into blood before it collapses.
Arachnotron: Each bullet you fire into the arachnotron removes a little bit of flesh. You stop firing when there is no more flesh on the metal apparatus.
Arch Vile: The arch vile does a little dance as you fill its body with bullets.
Cyberdemon: Bleeding from dozens of small holes, the mighty cyberdemon finally drops. You keep pouring lead into its head just to be sure.
Rocket launcher
Former Human/Sergeant/Captain/Commando: The former human becomes a rain of blood and guts.
Imp: Fire consumes the screaming imp.
Demon: Smells like beef...
Lost Soul: You think the lost soul whimpered before it was literally blown away.
Cacodemon: The cacodemon catches on fire and spins wildly as it loses height. It crashes into the floor and pieces of burning flesh fly around like shrapnel.
Pain Elemental: The pain elemental catches the rocket on the mouth, swallows it, falls and explodes into a shower of flesh bits, blood and sparks.
Hell Knight/Baron: You partially blast the hell knight/baron's head away. Its head looks like an anatomical profile sketch as it falls.
Arachnotron: The arachnotron's robotic parts explode as its ugly, screaming fleshy face is consumed by the flames.
Arch Vile: You blast the arch vile's torso away. All of its limbs fly in different directions leaving trails of blood and guts, while its severed head falls to the ground.
Cyberdemon: Your rocket meets the cyberdemon's own as it fires. When ensuing explosion clears, you see that the frontal half of the monster is gone. As you watch, its internal organs stop working, twitches one last time, and the beast falls forward.
Plasma Rifle
Former Human/Sergeant/Captain/Commando: You burn a few fist sized holes through the former human's body.
Imp: When the plasma stops glowing, you see the imp's severed arms, legs and head lying on the ground in a pool of blood. You can't see the torso.
Demon: The demon seems pathetic with its lower jaw trying to chew the air without the help of its upper counterpart.
Lost Soul: There's no proof that the lost soul have ever existed.
Cacodemon: You are greeted with the sight of a cacodemon burnt into two halves when the glow of plasma is gone.
Pain Elemental: The pain elemental looks distressed before explodes into blood, guts and sparks.
Hell Knight/Baron: You can see that your plasma rifle has burnt a clear hole through the hell knight/baron's chest and further shots are just passing through it.
Arachnotron: The robotic parts of the arachnotron spark and smoke under plasma fire as its ugly face looks alarmed. Just a split second before it blows up, you see its ugly face is contorted with terror.
Arch Vile: The plasma fire burns through the arch vile's knee. It topples down, bringing its groin to the spot where its knee used to be. The plasma burns through that too as the lanky demon howls in a mix of terror and rage.
Cyberdemon: You flay the cyberdemon's huge face with your plasma rifle. It gives you a skeletal grin as it falls.
BFG
Former Human/Sergeant/Captain/Commando: Not only the former human becomes red rain, but it also evaporates before it can rain much.
Imp: The imp's flesh burns away in an instant. A split second later, its charred skeleton shatters and the thing is completely gone.
Demon: The demon explodes like a firework made of flesh. The bloody bits are also burned a moment later before they can fall to the ground.
Lost Soul: The lost soul definitely whimpers before it is instantly disintegrated.
Cacodemon: The cacodemon's exterior burns away, revealing a huge bone cage that may be its skull. The charred bone sphere falls to the ground and shatters into a million pieces.
Pain Elemental: A huge ball of green plasma as big as itself hits the pain elemental. The following explosion of plasma has a sublte red tint.
Hell Knight/Baron: The hell knight/baron covers its head with its arms and crouches in an attempt to survive the plasma explosion. It fails.
Arachnotron: The arachnotron's fleshy face can't even react before it burns away. The robotic parts explode shortly afterwards.
Arch Vile: You can see the arch vile's skeleton through its body as it embraces the huge green ball of plasma. Then the plasma ball explodes and it rains arch vile.
Cyberdemon: Even the mighty cyberdemon looks worried as the huge plasma ball flies toward it. You can't look as the plasma explodes but when you look, the cyberdemon stands triumphantly. Slowly its grin fades as it realizes that there's a cacodemon sized hole through its enormous chest.