252 HP/252 Atk/4 Sp. Def
Clefable's base Attack stat of 70 is none too impressive. In spite of that, however, there's not much other than Ghost-types, Rock-types, or Steel-types that will like being on the recieving end of a STAB and Life Orb-boosted Double-Edge, especially when the user isn't taking a single hit point of recoil damage. ThunderPunch and Ice Punch make up the dreaded BoltBeam combo's physical counterpart. SoftBoiled is, of course, for easy HP recovery.
The ability of choice? Magic Guard, hands down. Unaware is a useful ability, but Clefable looooves its recoil-free Life Orb Double-Edges. Not even at gunpoint should you consider using a Clefable with Cute Charm. Well, OK, maybe at gunpoint. Depends on how serious the person with the gun is about such a strange demand.
252 HP/252 Atk/4 Sp. Def
~Trick/Belly Drum/Brick Break
Magic Guard comes in handy once more, allowing Clefable to poison itself with Toxic Orb without incurring the damage that comes with it. Facade, under the influence of the bad poison, reaches a base power of 140- and that's without STAB! Softboiled is for the damage Clefable is likely to take from its opponents. Ice Punch is so ghosts don't totally wall you. And, as has been the case for many Pokémon in the past, 4-moveslot syndrome rears its ugly head. Clefable can run several moves in that last slot. Trick allows Clefable to foist its Toxic Orb upon an unsuspecting foe (and with luck acquire a Life Orb in the process), thereby badly poisoning them. Belly Drum allows Clefable to maximize its otherwise iffy Attack stat, but this WILL damage Clefable, so be careful. Brick Break is good if you're worried about freakin' Steel-types. Normal+Ice doth not good coverage make.
Again, Magic Guard is the obvious choice here, as it prevents the damage from the poisoning from the Toxic Orb.
252 HP/200 Def/52 Sp. Def/4 Sp. Atk
If only Clefable got Psycho Shift, this would be for all intents and purposes identical to Sigilyph. And I know for a fact that Sigilyph with a set like this can and most likely will cause complete and utter chaos. Anyway, Cosmic Power ups Clefable's defensive stats, allowing it to take hits like a tank. Stored Power gains power from said defensive boosts, allowing Clefable to hit like a tank. Softboiled restores Clefable's health so it can continue to take hits and dish 'em out like a tank. And the last move is up to you, but they all serve the same purpose- burn the opponent. Sigilyph achieves this with Psycho Shift, but as I stated earlier, Clefable was not blessed with that option. So in this case (barring getting an opportunity to use Trick a second time), this last move will be a one-off burn. The Flame Orb also burns Clefable, protecting it from more debilitating status, such as paralysis and freeze.
Magic Guard. 'Nuff said.
252 HP/252 Sp.Atk/4 Sp. Def
Weather you like it or not, weather is a large part of today's competitive battling scene. This Clefable set was slapped together with that in mind. Thunder fries the Water-types of an opposing rain team. SolarBeam and Fire Blast take advantage of the sun. Softboiled... well... you know the drill by now. Also useful on your own sun or rain team, and a nasty little surprise should your opponent change your sun to rain, or vice versa. As a bonus, Magic Guard (in addition to preventing Life Orb recoil) stops Clefable from being damaged by Hail or Sandstorms.
252 HP/252 Atk/4 Spd
We've all had that moment where a Glare/Headbutt Dunsparce swept our teams. Well, not me. I was usually on the other end of such sweeps. But I digress. Between the paralysis of Thunder Wave, the confusion from Swagger, and the flinch chance from Headbutt, good luck with your opponent being able to strike back. Almost completely walled by Ghost-types (I say almost because of confusion damage), but nothing's perfect. Softboiled is obvious.
I was considering recommending Unaware for this set, but it would be illegal with Headbutt. Magic Guard.