Okay, I know I posted a potential special moveset here earlier that included using the Poltergust 3000. Here's how I think it'd work.
I think it'd work like Mr.G&W's Down B.
When some kind of projectile is fired at Luigi and you press down-b, he pulls out the Poltergust for a second and will suck it into the vacuum. After you collect so many projectiles, preferably 3, it will become full and when you press down-b again it can send out (randomly):
Fireballs: Causes burn that lasts about 3 seconds (dealing 10 damage/ second with low knockback).
Iceballs: Has high chance of freezing opponent (deals 20 damage on contact with mild knockback).
Waterballs: Makes your character slippery (deals 10 damage on contact with high knockback).
OR
Some kind of ghost that flies foward and hits the opponent with mild power and high knockback. It then disappears.
Comments?