The Gargle Blaster is a common running in-joke among several Tabletop Games groups, featuring such novel notions as alcohol proofs greater than 200 (such as the distilled vodka "357", which is somehow 178.5% ethanol) and a drink known as "Engineer's Entropy", which is so potent, it must be stored separately from other alcohol, handled with tongs, and served in a reinforced crucible. At worst, it causes instant death. At best, irreparable liver damage and a round of applause.
Warhammer's goblin fungus beer allows goblins (more or less a human-child in size) to easily swing around metal balls bigger than them. It also makes them meaner and crazier, and you're never sure where they are going to impact.
Warhammer 40,000: Fenrisian mead is said to give Space Marines hangovers like continents colliding. One can only wonder what they would do to the biological systems of non-genetically-engineered human individuals. One of the ingredients is jet fuel, so...
Ditto Macraggeii wine.
In Tales From The Floating Vagabond, the house special at the eponymous Floating Vagabond is called "The Singularity", which only the Floating Vagabond's bartender knows how to mix without killing the person ordering it. There's a random table you roll on whenever you drink one. Some of the results from that table include "Imbiber instantly goes to maximum intoxication stage", "Imbiber is temporarily taken over by a past life", "Imbiber grows extra limbs", and "Imbiber's clothes come alive and gain sentience".
BattleTech has the PPC, named after the Particle Projection Cannon, because it can "take your head off". Two shots of Everclear with your choice of either a shot of Peppermint Schnapps (Steiner), Tequila (Davion, Capellan March), Bourbon (the rest of Davion), Ouzo (Marik) plum wine (Liao), sake (Kurita), or MORE Everclear (Periphery)
In the Tol Galen LARP/tabletop system (played only in the Channel Islands and filled to the brim with references) there are a few of these, the best established being Goblin Krakk (named for puns and the ballistic missile warhead from Warhammer 40k) which is made from adding white powdered substances to berry juices and fermenting however you can; it causes literal brain rot. The most recent addition to this list is called Surt (after the norse fire giant destined to engulf the world) that was invented by accident when Blackwatch (a mercenary company with a hideously complex corporate structure that borders on SCP Foundation levels of protocol) sent the recipe for its existing gargle-blaster called Reaver (Brewed up by the poison department as a beverage strong enough to hide the taste of the hideously powerful combat drugs Blackwatch constantly trials on its forces, named after the Firefly characters that also inhabit our system as the virus) to its "Alternative power sources" division, roughly translated as the people who want to build weapons that make magic obsolete. The name for Surt is derived from the fact that the recipe was created on the containment site of an Utsuho expy and related materials contaminated the first batch. When the first bottle was opened the artificial atmosphere ignited and almost led to a major containment breech. To cut a long story short, there is a drink in our system with the same properties as a thermobaric weapon.
Changeling: The Lost has the Brewer Kith of the Wizened Seeming — basically, changelings who were put to work mixing reality-bending concoctions for the enjoyment of the True Fae. These were the guys who made the cider that knocked out Rip Van Winkle, and it shows — their Kith blessing is the ability to spend a point of Glamour and turn any liquid into an alcoholic concoction. Even at the lowest levels of their power, it's still possible (through very lucky rolls) to create a drink that can knock a man unconscious in one gulp. There's a special Contract only they can get that lets them do this without even touching the drink in question...Which doesn't sound too useful, until you realize that you can do this with ANY drink you're close enough to (Faerie healing elixirs, a Hunter's Buffing Potions). Need to get a guy to spill a secret? Sit across the room, wait for him to take a drink of just about anything, and BOOM, he's spilling his guts.
The D20 Guide to Alcohol (a third-party D&D book), has an entire section composed largely of these. One of note is Minotaur Malt Liquor, a beer that can literally put hair on your chest, and horns on your head. Get smashed off the stuff and fail your save? Congratulations, you'll be a minotaur by this time next month.
The GURPS Dungeon Fantasy supplement Taverns contains special drinks that are either Booze-Based Buff, or this. For example, drinking the Vorpal Brew will cause one point of damage to you unless you already have alcohol in your system, and Wight Wine will give you a level of Fearfulness for a random amount of hours.
Shadowrun features Hurlg, a beverage described as "a dark, thick ale the consistency of soup, swimming with hops and nutmeg". Humans and elves without special implants or toxin resistence spells suffer from painful stomach cramps when they drink it.