Mamoswine

Mamoswine's STAB combination hits almost the entire OU metagame for neutral or super effective damage, making it an excellent wallbreaker that can fit on a variety of teams and is difficult to deal with defensively. Ice Shard enables Mamoswine to also check many of the metagame's top threats, such as Landorus-T, Latios, and Garchomp. Thick Fat is also decently useful, especially if Mamoswine is used on a rain team to further reduce its Fire weakness. Mamoswine has subpar defensive stats and is weak to a lot of common attacks, which can make it hard to bring and keep in play. Its Speed is only decent, which makes it rather easy to revenge kill with faster Pokemon that aren't weak to Ice Shard unless it is behind a Substitute.