Doom
The granddaddy of the first person shooter, the original ass-kicking demon-slaying 3d slaughterfest, Doom is a franchise that demands respect even in the hallowed halls of /tg/.
Minimalistic in plot, Doom is easy to grasp; you are a Space Marine (no, not the 40K guy, a jumped-up soldier who is sent to fight on other planets, so closer to the Imperial Guard) stationed on Mars. Somehow, demons break through into our reality and slaughter everyone else on the planet. Your job? Fight your way to where, you hope, there's a ride off of this rock, and make bloody mincemeat out of everything standing between you and salvation. Standing in your way are armies of zombified fellow marines and eggheads, fireball-tossing imps, hulking flesh-eating demons, cyborg-demon monstrosities, and various other hell-spawned nasties who want to kill you horribly. Good luck. You'll need it...
Although not the very first of the FPS genre (that goes to its predecessor, Wolfenstein 3D), Doom was definitive to the genre, so much so that "Doom Clone" was the standard nickname for many years afterwards. And, for the time, it was incredibly dark and gory. To put it in perspective, there's still people playing it and hacking around with the source codes for it to make funner games to play - there's even a monstergirls modhack being churned out, complete with hand-drawn artscenes and a complete revision from "kill the demons" to "fuck the demons into submission". Hell, Final Doom is a compilation of maps made by two out-of-company designers made just because they could in the 90's!
According to the latest iteration of Doom, the Doom Marine has been tearing up demons from not just one, but multiple realities, becoming a literal boogieman for the forces of Hell. In that case, the Chaos Gods better hope that Doomguy never finds his way into their reality, or else they'll quickly learn the true meaning of Rip and Tear. After all, they've got enough of guys like him as it is!
Adaptations
Vidya
The original Doom was fast-paced and bloody, but not afraid to take breaks for scares, either; there's some really creepy levels in there. Doom II, meanwhile, was even faster-paced, a circle-strafing explosion-rich gorefest that defined the game and the FPS genre in the eyes of its fandom. Plot was bare-minimum: Demons took over Phobos and ate Deimos, kill them all. Or, in Doom 2's case, Demons are trying to infest Earth in revenge, kill them all AGAIN. But this time, it's personal. (No, seriously, they killed your pet bunny Daisy.) There were some other adaptations, an N64 port that played up the scary and Final Doom for the PS1 which had a bunch of fan maps being the most significant of them.
In the early 2000s, Doom 3 came along, following in the example of Doom 64 (the little-remembered N64 port) as a slower-paced, creepy, almost Survival Horror themed game. The plot tries to be a bit deeper, with this prophecy about an alien weapon capable of killing the denizens of Hell once said denizens break out of a UAC portal. There was an expansion pack/semi-sequel in "Resurrection of Evil" that follows up a bit later with an unethical scientist trying to get his hands on an unholy artifact while the new PC tries to keep it out of Hell's hands. Altogether, Doom 3's not a bad game, but it's not the same action-packed thriller that people were expecting after Doom II, wasn't nearly as mod friendly, and Doom eventually went back into obscurity.
Then the latest Doom came out in May 2016. This rendition can basically be described as "3d Brutal Doom II" only sexier, with features like ripping enemies apart with your bare hands and having to stay on the move to avoid being torn to shreds. The plot is also about as bare minimum as the original, kicking the player straight into the action with waking up on Mars, immediately smashing a zombie’s skull, and basically being told “demonic invasion, go kill everything.” Also, the player this time around is someone the demons call the “Doom Slayer", who has traveled through “Worlds and Time” (hinting that this Doomguy could very well be the original Doomguy from the first two games, having also survived Doom 64 and has been traveling Hell since), and millennia ago kicked Hell’s ass so hard that the best the demons could do is seal him away so that he wouldn’t destroy Hell. Then the UAC decides to deal with an Energy Crisis by quite literally slamming an Oil Derrick on a Hell Portal and siphoning off Hell Energy for power, starts stealing artifacts and treasures from Hell and ended up dick slapping the Demons as they defile an unholy temple and taking the Doom Guy's prison. After that the demons saw that the Doomguy’s prison/tomb was empty and the invasion was actually a panicked attempt to stop the Doomguy from being woken up. Either way, demonkind collectively shits itself as the Sealed Badass in a Can is unleashed to Rip and Tear once more.
No, seriously, you're told to "Rip and Tear until it is done" in the opening narration.
The original was very mod-friendly in its day, and several mods and fan-games are available for the first two titles. One of the most famous is the Brutal Doom mod, that ads lots of dismemberment and gore to the game, but also a number of gameplay tweaks to give weapons useful trade-offs rather than each being a strict upgrade of the last, and "Glory Kills," melee-based finishers (then known as "fatalities" - yes, there is Sub-Zero's "rip skull along with the spine" finishing move). There is also Doom the Roguelike, which somehow does a very good job of merging the notoriously cerebral and complex gameplay of a roguelike with the fast-paced demon-blasting of Doom into a surprisingly successful experience. Both included elements that were grafted onto the May 2016 Doom.
Comic
The only thing you need to know about it is that it's a masterpiece of absurdity and comedy that only the 90's could make. Sure, it's only one issue that was released back in the days of the first games, but each page of it was just that fucking STUPID that you had to see it to believe it!
Board Game
Yes, there is a Board Game - made by Fantasy Flight Games no less - giving the vague '/tg/ related' qualifications this site uses. It was released around the time Doom 3 was released, though it wasn't that remarkable and is pretty hard to find nowadays.
One guy plays the baddies, the other 1-4 players play a band of unfortunate marines. The heroes start with 2-3 powerup cards, and the baddies get 5 cards from his own deck and during the game, he gets to draw more (the rate of which is equal to how many marines there are) and if his deck is empty, he gets to insta-kill one of the Marines. His guys are more varied in their movement but they can only shoot once.
The marines have three options: move 8 spaces without shooting, move 4 spaces and shoot once, or shoot twice without movement. They need to explore the board, find computers and other events as the board provides. The baddies, meanwhile, can either upgrade his monsters or bring more to the board. Either way, his goal is to score 6 kills on the Marines.
Movie
Also (roughly) around the same time as Doom 3 was a movie starring Karl Urban and former WWE superstar Dwayne "The Rock" Johnson. It pretty much replaced the whole Hell plot with some genetic experimentation to give people superpowers that only succeeds in creating hyper-aggressive mutants, and a squad of Marines sent to investigate the mayhem. It wasn't that good, with the only really 'good' scene being this one scene where it's all FPS-style like the original games and has monster killing.