I tend to lean more towards the silly side of things as opposed to useless.
Flagellant's Whip: A regular whip that, when used against the wielder or an ally of the wielder, buffs the accuracy and AC of the wielder and all nearby allies.
Performer's Slippers: Slippers that grant the user amazing dancing and instrumental skills when worn. They depict a pair of pink rabbits.
Banana Bunch of Wand Summoning: Can be used to summon a random wand. Wand's effects are random, and can range from summoning eldritch horrors to flinging crocodile ghosts.
Pendant of the Inebriated: Causes the wearer's emotions to fluctuate wildly. +2 bonus to intimidation checks. Side effects include shamelessness, inability to ride a horse, dizziness, difficulty walking in a straight line, slurred speech, and occasional vomiting. Should not be worn during pregnancy because of the risk of birth defects.
Flask of the Inebriated: An enchanted flask has the magical property of turning water into cheap ale.
Crown of the Inebriated: An accursed crown that, when worn, allows the user to control the minds of all sentient creatures in a 200 foot radius that have more than 0.1 BAC. User must also have more than 0.1 BAC for crown to work.
Ring of Obscurity: The wearer develops an appreciation for indie music, films, and games that are of decent caliber but are underappreciated.
Daemon's Eye: A really cool treasure obtained from killing a hellish archfiend. It doesn't do much at all, though.