PrC: Frenzied Berserker from Complete Warrior, Ur Priest from Complete Divine, Initiate of the Sevenfold Veil from Complete Arcane are all pretty tough. Mage of the Arcane Order is somewhat broken when allowed for a sorcerer (depends a bit on the campaign style, however). Most of them are ok, tho, IMHO.
Some folks dislike Assay Resistance from Complete Arcane, since it is highly superior to the Spell Penetration feats in many situations (I don't think it's too bad, tho).
The Quill Blast spell from Complete Divine is whacky.
All those conjuration spells, which have been mentioned, make the evocation school seem kinda superfluous, that's right.
Divine Metamagic is ok, as long as it is not combined with Persistent Spell or Quicken Spell.
Bye
Thanee