Soul Whip

Soul Whip is a  weapon added in the 0.9.10 update. You cannot cast the rod for this item, as it will shoot the beam instead.

The Soul Whip does however require level 26 even though it isn't used for fishing.

This weapon can be converted into a dungeon item with Wither Essence.

This sells at the moment for about 20 million coins.

Usage
The Soul Whip can be used as a melee weapon or a ranged weapon.

When its ability is used, it shoots a beam in the direction the player is aiming. This beam has a parabolic trajectory, travelling forward 13 blocks and upwards 2 blocks. The beam travels through enemies, damaging all in its path; for the first 3 enemies hit, it deals its melee damage, then it is halved for every subsequent enemy hit. The ability does not consume mana, but has a hidden cooldown of 0.5s. Holding right click will continuously activate the ability.

Essence Crafting
This sword can be upgraded with wither essence. Once converted, it requires Catacombs level 23 to use.

Trivia

 * It's considered by some to be the best weapon for grinding Ghosts, as it provides a way of damaging them without getting into their range.
 * The beam follows the curve $$y=-\frac{8}{169}(x-6.5)^2+2$$.
 * When swapping to this weapon from a fishing rod with the bobber out, the bobber will remain out. The bobber will not be reeled in when right clicking with the Soul Whip, but will be when swapping back to the rod.
 * does not work on enemies killed by the beam.