Garchomp (F) @ Garchompite (If not Gen VI: Soft Sand)
Trait: Sand Veil (Mega Garchomp: Sand. Force)
Nature: Jolly (+Speed - SpAtk)
EVs: 252 Atk / 252 Speed / Whatever's left
-Dragon Claw: (Type: Dragon / Power: 80 / Accuracy: 100) STAB, and covers dragon weakness.
-Poison Jab: (Type: Poison / Power: 80 / Accuracy: 100) Covers Fairy weakness, slight poison chance.
-Earthquake: (Type: Ground / Power: 100 / Accuracy: 100) Perhaps the most important move for a Garchomp. Mega Garchomp's Sand Force, combined with STAB, can cause some serious wreckage. Also covers Ice weakness.
-Sandstorm: Extra evasiveness, and for reasons explained above. Plus additional damage to the opponent.
I hope this helps you as much as it did me. Thanks for reading!