Regigigas @ Leftovers
Ability: Slow Start
Nature: Naive (+Speed, -Sp. Def.)
-Zen Headbutt (Coverage for Fighting types)
-Revenge (This is a good move, because of the Slow Start ability)
-Crush Grip (STAB, signature move of Regigigas)
-Fire Punch/Thunder Punch/Ice Punch (Good power, Physical bonus)
*You can replace Revenge for Payback, because it's super effective against Ghost type Pokemon and it's Slow Start ability.