Can be one of the biggest threats in the game. Have a tank or wall with a good ability such as Cresselia use skill swap on him. Cresselia uses special attacks and won't mind the speed drop. Regigigas would now have 2 immunitys and only 1 weakness plus 160 base attack. If you can get Belly Drum passed from a Smeargle, (alongside a Mean Looking Sleep inducer.) Then there is no way that you could not sweep a team. The best move set would be Superpower, Earthquake, Ice Punch and Thunder Punch!