I'm thinking out loud here, not having a particular direction in mind at all
game start el-cheapo - Aristocrat and/or Mercantile feat need an extra suitcase
Special Materials - cost say x10 what a normal axe or horse or backpack, and might make a difference in early levels
+1 to +5 weapons - quite the yawner and duplicates just 1 of a full caster's spells
other spell mimics - quite the yawner and duplicates just 1 of a full caster's spells
Golf Bag - a small pile of stuff , usually for classes that are on the Monk or Fighter side of things
Standard Items - does something interesting without breaking the game
Intelligent Items - not much further beyond an unbroken Custom Item , some just spell mimics
Class Fixers - any small pile needed to fix the Monk or Fighter etc ...
spell mimics with extra sauce - quite the yawner for experienced players but overpowered otherwise
Epic Items - vaguely here , but more likely in other categories
Class Upgraders - Skillful weapon enhancement , Divine Power item , Torc of Power Preservation / other recharge items
Custom Magic Items - usually massive upgrades , some very broken
Artifact - only in game due to DM Fiat or very high level divinations. Generically stronger than +6 items.
loophole makers - Candle or unedited Strand , stronger than Artifacts but don't tell the cupcakers
EDIT - reordered the list around general power levels
Ideas ??
Maybe some of these categories can be combined. I probably missed a few categories.