My favorite vibrator for tickling is a silver "power egg" coated by soft plastic which is shaped like an elephant's head, complete with trunk and tusks. That means three vibrating tips are tickling the hell out of any victim. I call it my "ticklephant". 😛
Anther nice item I have is a self-construed vibro-feather: I took a vibrator with a bent tip for G-spot stimulation and fixated a stiff pointed goose-feather to it, on two different spots of the stem. Thus, the vibrations get transported directly to the feather tip, and at high speed the tip moves so fast that it's almost invisible. That thing usually works even on less ticklish people, particularly in the armpits and between the toes. Simply great!