This is just my opinion but Muk is by far the best pokemon in NU to use with assault vest! Here is my set:
Muk @ Assault Vest
Nature: Adamant
Ability: Poison Touch
Evs: 4 Hp/ 252 attack/ 252 special defense
Moves:
Gunk Shot/ Poison Jab
Rock Slide/ Fire Punch
Shadow Sneak
Ice Punch/ Power-Up...