9. Trousers of shrinking. Their only power is to magically change their size to fit someone who's one size category smaller than the person trying to put them on.
12: Paddock of the Titans: A great green field where several titans wander about.
13: Ring of laser globe of invulnerability: render the wearer immune to all manner of light amplification by stimulated emission of radiation. Sadly, no weapons in D&D inflict damage by amplifying light with stimulated radiation.
14: Seven League Boots: No amount of ice can help the tremendous groin strain that you get when you put one foot 24.5 miles ahead of the other...
Here's a few that I actually have in Akin's 'The Friendly Fiend' magic shop (in Sigil). It's the only magic shop in my campaign and everything he carries is pretty pointless:
15. Vampire Goggles - protects a vampires eyes from sunlight (but not the rest of its body)
16. Cigar of Everburning - Cigar is always lit on fire but doesn't burn, isn't hot, & the tobacco isn't real (but you'll look cool).
17. Quill of Calligraphy - Have sloppy handwriting? This quill writes in a beautiful calligraphy style.
18. Bandanna of Ever-Present Perspiration - Cools down body temperature but causes unstoppable sweating.
19. Halberd of Rat Slaying - +5 enchantment bonus vs rats.
20. Cloak of Indefinitely Blowing Wind - There always appears to be a draft blowing this cloak around (I had a player actually buy this for his rogue so he always looks amazing while standing infront of people).