Mamoswine

Mamoswine is a great check to many common Pokemon, including Dragon-types such as Garchomp and Mega Salamence, both of which are 4x weak to Ice; Steel-types such as Heatran; and Electric-types such as Thundurus and Zapdos. Its Ground / Ice STAB combination in is very hard to switch into in general because it hits many Pokemon at least neutrally. Most Ice-types are severely hindered by their typing, but Mamoswine can make good use of its Ground / Ice typing along with Thick Fat, offsetting its Fire weakness and Ice neutrality and giving it an immunity and resistance to the famous BoltBeam combination that many Electric-types carry. Mamoswine also has other useful moves, such as the always-handy Stealth Rock as well as Fissure to deal with defensive Pokemon it can't break through otherwise. Mamoswine is also very versatile. If your opponent predicts the wrong set, it can potentially cost them the game. One of Mamoswine's biggest downsides is its mediocre Speed, leaving it outsped by Pokemon such as Mega Charizard X and Y, Mega Kangaskhan, and Gengar. Mamoswine also has very common hard counters such as Cresselia, Rotom-W, and Suicune. These Pokemon can freely switch into Mamoswine, and there's not much it can do to punish them.