Human/half-elf assassin is hard to beat, dex warrior is a good choice for low ranks (would recommend human if not planning to level up, they get way worse at 51), giant warrior is awesome for pk in the 20s (and later if you do it right), duergars are also awesome if you're patient.

Paladin/shaman no longer require empowerment to be effective and can be awesome all the way from low ranks to 51.