Metagross@lefties (survivability is needed here, due to lack of HP EVs)
4HP, 252 Atk, 252 Spe
Claw sharpen
Meteor Mash
Zen Headbutt
Earthquake
Pair this with Baton Passing Zapdos, who can also help you deal with bulky waters and maybe even Skaymory before you begin your sweep. They've got very nice type synergy, although you will definitely need a reliable answer for fire types on your team.
That having been said, this should be able to function okay by itself. Not amazing, but okay. A rather interesting variation on this might be:
Metagross@Choice scarf
4 HP, 252 Atk, 252 Spe
Claw Sharpen
Meteor Mash
Earthquake
Trick
Use as a random scarfer on the first turn you use him. Bring him out again and use trick on their counter, who is hopefully Skarmory, or something highly crippled by choice scarf. If you have the jaw-dropping luck to have kept him in good health this whole time, you may then attempt a speed pass and claw sharpen sweep.