Hat of Disguise is amazing for its price.
Ditto goggles of minute seeing, +5 search for anything that really matters at half normal cost.
Amulet of retributive healing (MIC) iirc is 2000 gp and swift 3/day lets you heal yourself the same amount you just healed someone else!
Heartseeking Amulet (MIC) lets you attack touch AC 3/day as a swift and is dirt cheap, but hella broken and cheesy.
Boots of Agile Leaping (MIC) is 600 gp and lets you use dex instead of str on jump checks and if you have 5 balance ranks, stand from prone as a swift w/o provoking.
Wand chambers (Dungeonscape) are 300 gp, can be put in weapons and shields, and hold one wand. You are considered to be holding the wand when holding the weapon/shield and can activate it from inside.
Belt of Ultimate Athleticism (MIC) is 3600 gp and for the price of a swift action, lets you take 10 on all sorts of str and dex-based skill checks, including tumble, for the round you activated it. UNLIMITED use per day. You can also 1/day use it to take 20 on one of the covered skills' checks.
Dragon Mask (MIC) is 5000 gp to get See Invisibility for 5 min. per use 2/day as a swift action.
Brute Gauntlets (MIC) 500 gp for +2 on str checks and melee damage for a round 3/day as a swift, basically.
Chronocharms (MIC) various kinds, all are 1/day and 500 gp. Horizon Walker is a swift to move extra. Uncaring Archmage lets you cast a low level summon as a standard. Another is an immediate for +4 AC against an attack.
Steadfast Boots (MIC) are 2400 gp. By strict reading, they let you count as if you had readied to set against a charge 24/7, so if someone rushes you, you get to thwack him (for double damage!) even if you just had your turn and didn't ready anything. Even by a more toned down reading that it simply allows you to do double damage on a ready against a charge w/ any 2H weapon it's pretty sweet. Also gives stability bonuses.
Shiftweave vest (MIC) for 500 gp lets you swift action switch between 5 specific outfits, like a poor man's hat of disguise.