Imp sorcerer, pf.

[Rixx]

The Paizo staff have said that the monsters were not designed to be played, but to be fought. That's why that passage warns about letting PCs play as monsters - it's subject to GM approval, since some monsters have abilities that are way more useful in the hands of players than NPCs (The Hound Archon's Greater Teleport at will, for example).

They did say that if there's enough demand, they'd release a "Savage Species" type book based around a more balanced system for playing as monsters.