Bouffalant @ Choice Band/Life Orb
move 1: Head Charge
move 2: Wild Charge
move 3: Earthquake
move 4: Megahorn
ability: Sap Sipper
nature: Adamant
evs: 252 HP / 252 Atk / 4 Def
From using this guy I can tell you that he is a bulky monstrousity. He can take hits all day! I have personally seen him get hit by 3 supereffective hits and still have HP left. He is just a pure monster.
Granted he is rather slow with a base 55 speed stat, he still has 95/95/95 defenses and 110 base attack. With this in mind he completely destroys things with a Choice Band set and Sap Sipper.
Sap Sipper absorbs all grass moves, Leech Seed and Petal Dance for example, and for each one that is absorbed Bouffalant's attack rises 1 stage. With a Choice Band and 1 Sap Sipper Boost his attack rises to 787 with this set. This makes him a complete counter to Lilligant, Cottonee and any other grass pokemon.
In RU most of the things that countered him are gone, but you might still want to use Life Orb over Choice Band for Ghosts that would end your sweep.