Mamoswine

Mamoswine is one of the very few Ice-types that stand tall in the DW metagame due to both its typing, which grants it a neutrality to Stealth Rock as well as an immunity to both hail and sandstorm, and its fantastic offensive coverage, which allows Mamoswine to solely rely on its STAB moves in order to crush the opponent. Our shaggy friend also has a mammoth (excuse the pun) base 130 Attack, which basically translates as "whatever doesn't resist its moves will get pulverized." Its Dream World ability, Thick Fat, grants it a neutrality to Fire and a resistance to Ice, making Mamoswine one of the few Pokemon that resists the famous BoltBeam combination.

It's not all good news for Mamoswine though. It has a slew of weaknesses to common types including Fighting, Water, Grass and Steel. Furthermore, base 80 Speed often just isn't enough for the fast-paced Dream World metagame, and a weakness to common priority moves such as Mach Punch and Bullet Punch is unfortunate. However, don't let this put you off from using Mamoswine because it's a very powerful Pokemon and an excellent answer to fast and dangerous threats such as Garchomp, Dragonite and Thundurus that lurk the tier.