Why does this exist

[Black Waterfall]

That's a good question @RetroTyphlosion. The best answer I found was this one on pokemondb.net:
 

Quote:The main one would be to Trick or Switcheroo the item into the opponent to make it susceptible to a certain attack. This is incredibly gimmicky and really there are better items to use, but this could have some use in doubles where a fast Pokemon would switch the item onto a Pokemon like Gliscor and then its partner, who moves next, uses and Electric move. Of course just using an Ice moves right away is the batter solution, but it is one way it could work in at least some way.

The other, much less viable options would be:

Using it to play with Pickpocket users. Pickpocket is uncommon and can get you unwanted items like the Ring Target in the first place, so don't expect this to work well unless some guy is dumb and uses it on his Weavile.

Intentionally using it to allow certain contact moves to hit you, and you have the ability Iron Barbs or Rough Skin. For example, take a Ferrothorn with Iron Barbs. If a guy for some reason tries to use Cross Poison is something on it, it would take damage from Iron Barbs because the moves makes contact. This is such an unlikely event that you can basically forget it. The result, 1/8 of your opponent's HP gone, isn't even worth it anyway. It has some uses, but really nothing notable. It you want to mess with Gliscor and Ferrothon, give them a Scarf or something. They won't appreciate it.

but those definitively are far from reasonable motivations for using it.