Game Breaker: Thermite the thermonuclear termite is basically all you need in the game after you acquire him (to be fair, he's the last warrior you get.) He can also shoot napalm and an upgrade lets him shoot trolls, which for some reason explode.
Ash and Thermite are healed by fire. Spend 3 Elemental fruit for Ash's "Incinerator", and stand in it to Heal Thyself without boxes.
Deep Blue's water jets are very adept at knocking enemies into pits and water, which is instant death for them. It's also a great way to get combo points.