Railgun

Description
The Railgun is an upgrade for the Power Tool that can be modified in the TInker Table to propel a projectile. This projectile provides a heavy knockback depending on the amperage setting in the Tinker Table. This knockback can be anywhere from 1 to 20 blocks, and repeated firing can launch a player from bedrock to higher than 200 blocks. The fall would be deadly if you do not have appropriate protection.

The blast will one shot MOST mobs when on its most powerful setting. You must have a clean line of sight to your target. It appears that water may dampen its effectivness.

Source(s)

 * http://machinemuse.net