Maledict in ROE. A more adrenaline-pumping fight you have to look for.
Crowning Level Of Awesome: Doom 3's rendition of Hell. Unlike the original Hell levels, which were pretty much like normal levels only with stone walls, a red sky and a lot of blood splashed around, the Doom 3 version is a warped Fire and Brimstone Hell floating in an endless dark void and filled with nightmare imagery. The art design is amazing. You're also robbed of all your equipment, including your damn flashlight, so there's no comfort from the darkness and the only light you will see is the red of infernal flames.
By the end of Doom II, once the Big Bad Icon of Sin (John Romero) gets iced, the epilogue states how it trashed hell in its death throes. Say what you will but the result of that is that the Marine himself, the player has effectively and indirectly DESTROYED HELL
The Marine from Doom 3: Resurrection of Evil has one too. When Maledict/Dr Betruger, the commanding demon of the hellish forces, demanded him to give him the Artifact, The marine instead shoved it in its throat, killing it. If the marine died as well is today unknown.
A meta-example would be beating any of the Nintendo Hard megawads at all, especially Deus Vult.
In may be funny to telefrag an enemy accidentally but it's both funny and completely awesome to telefrag a Cyberdemon or a Spider Mastermind.
Brutal DOOM introduces "Rip and Tear!" on the berserk back, allowing you to perform Mortal Kombat-esque executions on enemies from ripping off a sergeants head to tearing out a baron of hell's spinal column with the head attached.
v18 introduces a new fatality for the sergeant to wrench his shotgun away, stab him with it like a spear and then blast him into the air with the gun itself.
QuakeCon 2013 Doom 2 (multi-player) Tournament is a nice call back in itself. But one of the real moment of awesome came during first round of the finale between Devastation and Jkist3_ as they go at it for $1,000, trading buckshots and BFGs on almost one-for-one basis. Then Jkist3_ pulls out a draw when Devastation unfortunately spawns right in front of him and ate a faceful of pellets IN THE LAST EFFING SECOND!!
Say what you will about the Doom movie, but the first-person action sequence near the end of the film was made of all sorts of win.
That scene was one of the two things that paid for the ticket, the other being The Rock's line:
"I was not supposed to die!" *gets dragged away*
The Rock bursting through the glass panel and shouting "SEMPER FI, MOTHERFUCKER!"