Regigigas paired with a worry seed pokemon is a good combo. Making regigigas's ability insomnia means that its slow start ability will no longer cut its attack and speed in half, which is his bane. Pokemon like cradily and ferrothorn learn this move so it wont be that hard fitting a regigigas on your team. The only true problem here is that you shouldnt place regigigas at the beggining, because worry seed could eliminate other abilities.
(Worry seed doesnt work on pokemon with the abilities multitype or truant)
(Worry seed doesnt work on pokemon with the abilities multitype or truant)