I've recommended this before, and I'll do it again!
Sableye @ Leftovers
EV's: 248 HP / 124 Def / 136 SpD
IV's: 0 Atk
- Foul Play
Of the leads listed here, Sableye cripples, puts a stop to, or at least forces a switch from the following: Terrakion, Espeon (which is hit by Foul Play), Mamoswine, Machamp, Ferrothorn, Salamence (the physical moves, anyway), Landorus-T, Azelf (Rock-blocks), Genesect (U-turn crippling, as well as adding residual damage to wear it down), and Deoxys-D. That's all but 1 here, which is Celebi, who heals off Foul Play damage with Giga Drain.
Sableye puts an end to all hazard-setter leads, barring those with Mental Herb or Magic Coat (lookin' at you Deoxys-D). Sableye also halts riskier leads like Cloyster and Volcarona from setting up turn 1, and freezes non-Mental-Herb Ninjask in it's speedy little tracks. Stall teams leading with Forretress, as I've seen them commonly do, are put to a fullstop turn 1; putting stall to a fullstop is a handy trick of Sableye's in general. Throwing around burns adds boatloads of residual damage to teams all over the place, especially in conjunction with Stealth Rock switches, Spikes if you have it, and abilities like Ferrrothorn's and Garchomp's to make contact-hitters truly suffer. Burns also hurt Tyranitar and Hippowdon's attacks, and the overall lifetime of those two plus Politoed, making Sableye great for Sun teams. Breloom is left not knowing what to do against Sableye as well; should it Spore with the possibility of priority Taunt, or attack with the possibility of a priority burn?
If you know what you're doing, or want a little awesome on turn one, look no further than our favorite little ghost goblin.