Set: Life Orb Mamoswine

Mamoswine @ Life Orb 

Trait: Snow Cloak 

EVs: 4 HP / 252 Atk / 252 Spd 

Adamant Nature (+Atk, -SAtk) 

- Earthquake 

- Icicle Crash 

- Stone Edge

- Ice Shard 

With Icicle Crash, Mamoswine finally received a solid secondary STAB to back up its powerful Earthquake. In this metagame, it's a blessing to have a physical attacker that isn't walled by Gliscor. Mamoswine easily fits this criteria and also covers some crucial threats with its giant base 130 Attack and Ice-type priority.

Thanks to its powerful STABs and useful typing, Mamoswine plows through plenty of common OU Pokémon. Tyranitar, Jirachi and Gliscor are all cleanly OHKOed, while Rotom-W is easily 2HKOed with Stone Edge. Mamoswine's Speed isn't bad, either; this spread puts it at 259, which is fast enough to outpace a lot of common threats.

The type coverage this set provides is fantastic. Ice / Ground alone is good, but Stone Edge can be helpful for Gyarados and Rotom-W. Stealth Rock is also a viable option if you don't need the extra coverage. Ice Shard is a crucial priority move that allows Mamoswine to check Thundurus, Tornadus and Dragonite; it OHKOes all three after Stealth Rock. 

Mamoswine has issues with Skarmory and Bronzong, so be sure to include something that can deal with both. Heatran is a good choice for a partner, as it also handles Scizor reliably. Rotom-W can also work, thanks to its ability to heavily damage most Steels. Overall, Mamoswine is a heavily anti-metagame Pokémon that deserves more usage.