A really underrated Pokemon is Mamoswine. The best set I have found for him is this:
Mamoswine (M) @ Life Orb
Trait: Snow Cloak
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Icicle Crash
- Ice Shard
- Earthquake
- Substitute
It's just so powerful, and its STABs are so dangerous in Ubers. Here are some calcs: (yeah yeah they are pulled straight from the analysis but I WROTE the analysis so HA)
As shown, Mamoswine easily 2HKOes all three of the common physical walls in Ubers with a little help from Stealth Rock. It's not exactly slow either, and almost guaranteed to outspeed at least 2/3 of them even with Adamant. Nothing is a safe switch in for this behemoth except for Skarmory and Bronzong. The latter is almost never used, and even the former takes 44.3% - 52.1% from Icicle Crash if it has a specially defensive spread, meaning it will be 2HKOed with Stealth Rock. Even then, there's always the 30% chance to flinch. People never seem to realize how powerful this thing is, and switch in Groudon only to quickly switch out, getting heavily mauled in the process. Once they do realize how powerful it is, then comes the real fun. Put up a Substitute as they switch to a faster resist, demolish that, rinse and repeat. It even works as a great revenge killer for something like DD Rayquaza; it only takes 83.7% - 98.6% from a +2 LO ExtremeSpeed, so it can even revenge SD Rayquaza if you keep it healthy. That's such a waste of Mamoswine's amazing power, though. It really excels in tearing gaping holes in stall and offensive teams alike. Adamant is really needed over Jolly in my experience. It secures quite a few KOes, and Jolly outspeeds nothing over Adamant. Any base 90s that run enough Speed to outpace Mamoswine will most likely be using a +Speed nature anyways, so Jolly wouldn't even help. In short, Mamoswine is extremely powerful yet extremely underrated :(.