Notes:

http://www.smogon.com/smog/issue41/dont-use-that-use-this

Sometimes, the reason you shouldn't use a certain Pokémon isn't because it's necessarily bad, but because its job is much better done by some other Pokémon. Whether it be a better movepool, better stats, or a certain flaw one has, there are many Pokémon that simply just don't get to shine because one of the aforementioned is better used by other Pokémon. A good example of this would be how hard it is to justify using Jolteon over Raikou. Sure, Jolteon's high Speed makes it seem very appealing, but its overall low bulk makes it a bad choice, and Raikou is able to perform different roles such as being a special tank with an Assault Vest. As you may be able to tell, this article will feature various examples of Pokémon that are simply outclassed by others.

Undeniably, these are all mistakes and faulty Pokémon that newer players use when starting OU, and at some point or another, you may have been one of these players or have seen another player using these lackluster and outclassed Pokémon. In the end, this article may have helped you understand why certain Pokémon are just not worth it.