Technically speaking, Dragonlance Campaign Setting and Co. isn't 3rd party.
See, on top of broken stuff like Sorcerer Abominations, Reserves of Strength and the like, there's a chain of spells I found today, that are probably the most broken spells I'd seen yet.
I'm talking about 3 spells from Towers of High Sorcery (pg. 44): Arcane Staff (Lesser 3rd/Regular 5th/Greater 7th).
Effects:
Lesser (3rd) - place spell levels = INT/CHA modifier inside a Staff. Can store up to 2nd level spells.
Normal (5th) - place spell levels = Caster Level inside a Staff. Can store up to 4th level spells.
Greater (7rd) - place spell levels = INT/CHA modifier + Caster Level inside a Staff. Can store up to 6th level spells.
Problems arise when you either have a high CL, a high casting stat, or use Sanctum Spell to recharge it with itself... Now combine with the various spell restoring spells!
My own Sorcerer would realistically get 55 Spell Levels out of each 6th level slot at 20th. That's quite a bit, and with Versatile Spellcaster, could be even worse (...sure, why not let a Swiftblade store 18 Haste spells?).