Well, I think I can almost match JesterPoet's worse: this was also a 10 years ago 2nd edition game. Highlights of the horror:
-One player was playing a custom 2nd edition monk. Well, actually he was playing a human machine gun: through various rules abuses, he was able to let fly 80 shuriken per round. With Storm giant strength (from a girdle) for loads of damage.
-Said GM absolutely loathed this ridiculous farce, but would never challenge even the most abusive rules interpretation. Instead, he'd just have all the monsters attack the monk preferentially.
-An example of this: Party enters a room in a dungeon. (Monk is walking on the ceiling, invisible, directly over the party due to his magic items). 20 Bar-lungra demons ignore the entirely visible Paladin (weilding a holy avenger) and retinue on the floor to leap 30' into the air to attack the monk. All 20 of them. In sequence. And they got their full attacks, to boot. (Visions of dancing Bar-lunga demons...). And they could do this while still being 60' from the party underneath them!
-Other warpings of time and space occurred: in one module (Bloodstone mines) the main corridors are 8' high, 5' wide. The encounter in the module is with Stone Giants. We protest, since Stone Giants obviously can't fit throught the corridor! But no, the giants get to attack us. Two Abreast. To top that off, we were forced to remain in single file!
-The GM relentlessly followed the exact text of his (first edition) modules. Including treasure. So, a 14th level party with exactly 1 sword weilding character had: 1 Holy Avenger, 2 Frost Brands, 4 Flame tongue swords, half a dozen dragon and giant killer swords, and enough +1 & +2 swords to outfit an entire company of soldiers. The 3 mages had to suffice with a single Wand of Fear. With 5 charges. Wa-hoo.
-Later in the game (when it became clear that no logic nor balance applied to this game) I used my Wild Mage to really mess things up. Basically, I claimed as treasure: a Deck of Many Things, a luckstone. These, plus the Alternate Reality spell allowed for numerous amusing effects, like the ability to grant wishes pretty much at will to other party members (because Wild Mages could control the deck 50% of the time, and Alternate Reality could fix problems)
-This is in addition to things like the Cloud Castle, turning a High Priestess of Lolth to our side with a Helm of Opposite Alignment, Laser Wand Archers, and other rancid, smelly pieces of cheese we built up as the game went on.
Anyway, this game was incredibly silly. I'd never have played, except that I could find no other game to join.