Slowking
Nature: Modest
Moves:
-Surf
-Psychic
-Shadow Ball
-Calm Mind/filler
Surf and Psychic are must haves on Slowking, since he's a dual Water and Psychic-type.

So he'll get powerful moves that'll get STAB too.
Shadow Ball's for any Ghost-types, or other Psychic-types as well.
And Slowking could be pretty good once he's Calm Mind'd a few times, but you can keep Flamethrower in there instead of Calm Mind if you want.