First Idea: Railguns!
Does 100 damage(I know thats overkill, but it punches through anything it kills/destroys). Can be backpack or turret mounted. Uses 5-10 million EUs per shot. Destroys all blocks but bedrock.
Rails:
Barrel:
= Rail
= Lapotron Crystal
Backpack:
= Barrel
= Lap-pack
Turret:
Any other ideas?