I'll start. This is an old Arduin item customized and statted up for 3.0.

Whimsey Wine
(The Arduin Grimoire)

This potent faerie brew comes in different colors and tastes. There is no saving throw against its effects: when it is drunk, anything can happen – anything! This can be simulated by rolling on a 'whimsey chart' – every DM should have one – which contains at least twenty happenings foul and fell for the bedevilment and delight of your players. Here is a simple sample for use with this adventure; roll d24 (d12 + hi/lo die):

1-permanently add/subtract 1-4 points to Strength
2-" to Dexterity
3-" to Constitution
4-" to Intelligence
5-" to Wisdom
6-" to Charisma
7-" as a natural bonus/penalty to a random saving throw (d6): 1-2 Fortitude, 3-4 Reflexes, 5-6 Will
8-character physically ages/becomes younger 1d20 years, with no change in mental state (but characters who become younger past 0 can only be brought back with a True Resurrection, and physical stats can be effected profoundly either way)
9-character gains/loses 1d3 experience levels
10-character switches gender
11-character gains random new alignment (d10): 1 LG, 2 NG, 3 CG, 4 LN 5 N, 6 CN, 7 LE, 8 NE, 9 CE, 10 reverse of current.
12-character's head permanently changes to that of random animal (d6): donkey, boar, wolf, rat, parrot, or lion. As a freak, they gain a –8 natural penalty to all social interaction rolls, and while they can still speak in humanoid tongues they will sound like the animal in question while so doing.
13-character becomes permanently hasted or slowed
14-character permanently surrounded by Faerie Fire
15-character becomes permanently deluded that one characteristic is 8 points higher than it actually is: (d6) 1-2 Strength, 3-4 Intelligence, 5-6 Charisma
16-character becomes deluded that they are the long-lost heir to a kingdom or barony; 10% chance it's true!
17-character gains the use of a random arcane spell once per day as a special ability, caster level=character level; roll a single spell as on a minor scroll (DMG pp. 204 & 200). Sorcerors and bards gain this as a 'spell known' instead, but if they already know it gain nothing
18-character grows fully functional giant eagle's wings
19-character's legs become long, greenish, and web-footed: gains +12 racial bonus to Jump skill
20-character gains 1 level of Psion, as per Psionics Handbook; if psionics rules are not in play the character instead gains the ability to Detect Thoughts, usable at will
21-character's skin turns bright yellow, green, red, or blue (roll)
22-character turns permanently invisible, as spell
23-character instantly transformed into different creature: roll on reincarnation table in Player's Handbook p. 244 or (better) on Arduin's Random Reincarnation Chart, Welcome to Skull Tower, p. 25
24-going down the windpipe the wine turns either to Arsenic or to Ungol Dust (roll); character receives normal saving throws against the poison

A few of these results (permanent slow, e.g.) are on the order of character-breaking curses. DM's may wish to allow characters in-game recourse to eventually reverse some of the bad effects of Whimsey Wine, and conversely may eventually see fit to revoke certain boons. This is subject to DM adjudication, though in no case should magic of potency much less than a limited wish be efficacious in such efforts. Instantaneous effects, like statistic, shape, gender, level, etc. changes, should never be reversible except through more of the same kind of magic in any event.

Caster Level: 14th Prerequisites: Brew Potion, Wine-making skill, Confusion, Limited Wish, caster must have fey blood or be chaotic; Market Price: 4,900 gp.