Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 252 Def / 4 SpA
- Cosmic Power
- Stored Power
- Charge Beam/Moonblast
The great Cosmic Power Clefable is here pals! This set catches a lot of people who expect a CM set off guard. Clefable forces a lot of switches, so it's easy to get up the first Cosmic Power. After that, you're pretty much ready to rip to shreds any team not carrying LO Adamant Bisharp. Cosmic Power is the crux of the set, as it allows Clefable to improve it's bulk to insane levels. Soft-Boiled is much needed recovery. Stored Power, after enough Calm Mind boosts, destroys everything in it's path that isn't immune to it. In the last slot, you can choose between Charge Beam, which can boost Special Attack but leaves you harder pressed in beating Dark Types, or Moonblast, which lets you beat Dark types and hit for decent damage before setting up. An alternative spread of 252 HP / 120 SAtk / 136 Def can be run with a Modest nature to do more damage while still keeping some Physical Bulk, but it isn't recommended.
For proof that this set is fantastic, look to this tournament match where I (Wat A God) destroy my opponent with this set on a joke team.
Magic Guard is a great tool in Clefable's toolbox, but I think Unaware is something that is sorely overlooked on it. It's an ability that is pretty much exclusively used by Quagsire (Swoobat and Bibarel have it too but Swoobat does much better with Simple and Bibarel is... well, it's Bibarel), and Clefable's got enough bulk on its side that it could use it effectively. The set I chose forgoes healing for the sake of simply surviving hits with a combination of Def investment and Assault Vest to beef up its naturally good SpDef. I split its EVs in such a way that Ice Beam is a guaranteed OHKO on Salamence without defensive investment and very likely to OHKO a Garchomp that already has a little damage on it. It can counter pretty much any Dragon in OU, but it specializes in switching in on ones that will attempt to set up; a lot of them have moves that, with a Swords Dance or Dragon Dance boost, could potentially OHKO Clefable, but since Clefable's going to ignore their Att buffs, they could try and set up all day long and Clefable would just laugh in their little reptilian faces. Assault Vest allows it to easily survive most Special hits that come its way, and the combination of its Def investment and fantastic typing keep it alive through a lot of physical hits as well. Moonblast is obvious STAB and its best weapon against nearly anything not resistant to Fairy, while Shadow Ball combines with Moonblast for nearly perfect neutral coverage, Ice Beam hits harder against Dragon/Flying and Dragon/Ground, and Thunderbolt gives it a good weapon against Mega Charizard Y and Talonflame. You could swap Shadow Ball out for Flamethrower, but that'd leave you easily walled by Rotom-Heat, and wouldn't benefit much since Aegislash is already hit hard by Shadow Ball and Bisharp is just gonna kill with Iron Head anyway.
A few things to keep in mind is that, with the loss of Magic Guard, this version of Clefable can no longer come in to sponge up Toxic or Burn, and you'll give yourself away if the opponent has put up his own hazards when they see it take damage switching in. It also makes Clefable a bit less useful on sand offense. It runs best with Stealth Rock support so it can OHKO a Talonflame on the switch-in rather than having to take a Brave Bird and won't have to worry about Dragonite's Multiscale. It'd be a good idea to run it with something that has access to Wish as well since it's giving up Soft-Boiled and Wish for that Assault Vest. Wish Salamence would actually be perfect, particularly if the opponent has a pokemon you could trick into using a Dragon move or trying to set up on it. You'll more than likely want to keep it away from Bisharp, which can easily OHKO it with an Iron Head, and Mega Venusaur, which can eat up everything it does and 2HKO it with Sludge Bomb, but there's not too many other things I can think of off the top of my head it can't handle too well.