I think there was a Dark/Iron combo that made an Assassin ball. It goes through everything from the front but then stays at the back racking up a 30% backstabbing bonus. It basically just keeps doing backstabbing damage to everything from the back while you keep attacking the front. It felt really good.
This game is great by the way
Also, be sure to take egg sack if you ever have any Evolutions that leave things on the field (Magma, Glacier/Swamp) because when the egg sack breaks open, the baby balls that come out all become the field effect as well. It's really good.