I hope nobody has come up with this before because I spent a bit of time on it. Its not a new moveset, but a specially designed spread:
Mamoswine @ Choice Band
Ability: Snow Cloak
EVs: 112 HP / 232 Atk / 52 Def / 112 Spe
Nature: Adamant
- Ice Shard
- Earthquake
- Stone Edge
- Peck
This set was designed for one of my teams which had a fairly large weakness to Garchomp and Tyranitar if they got a Swords Dance/Dragon Dance. I needed a counter to both and I only had one available spot on the team: Mamoswine fits.
Switching into any Garchomp other than Chain Chomp, the strongest attack Mamoswine needs to be able to take is an Adamant Outrage from Scarfchomp.
Adamant 252 Atk Garchomp Outrage vs 112/52 Mamoswine:
62.98% - 74.04%
This ensures that switching into Garchomp's strongest initial attack, Mamoswine will survive even with Stealth Rock and one layer of Spikes on the field. He can then return fire with Ice Shard, which will OHKO any Garchomp that doesn't have 252 HP EVs and a large investment in Defense:
Adamant CB 252 Atk Mamoswine Ice Shard vs min/min Garchomp:
126.89% - 149.30%
Adamant CB 252 Atk Mamoswine Ice Shard vs 252/min Garchomp:
107.86% - 126.90%
You get the idea.
Alternatively, Mamoswine switches in on Substitute or Swords Dance; He beats either set simply by Ice Sharding. Swords Dance Chomp has to switch out immediately and Sub Chomp can only use moves weaker than Outrage if it doesn't want to get locked in and killed on the second turn.
As for Tyranitar, a CB Adamant Stone Edge does
80.21% - 94.34%. In return, Mamoswine easily OHKO's with Earthquake. Mamoswine can switch in, take the hit, and return fire before dying; His 112 Speed EVs get him 224 Speed, enough to outrun Adamant Tyranitar.
A Tyranitar who Dragon Dances on the switch in will do the same amount to Mamoswine with Stone Edge (less if the Tyranitar is Jolly), and can still be killed with Earthquake. As for BOAH, Mamoswine will switch in on the Sub, take
80.98% - 95.37% from the Focus Punch while he breaks the Sub, then outspeed and OHKO with Earthquake.
As a side note, while Mamoswine in no way counters Gyarados, if he can come in on a standard BulkyGyara before it gets a DD (unlikely, but possible), it outspeeds and has a good chance to OHKO with Stone Edge (
91.67% - 107.81%), and its a 100% OHKO with Stealth Rock. He also can't take Heracross 1-on-1, but Peck does
106.31% - 125.25% to a min/min 'Cross switching in. Peck could be replaced with Avalanche or Ice Fang if you'd prefer a stronger STAB Ice attack.
And that's my anti-Chomp, anti-Tyranitar Mamoswine. Obviously it works best with Wish support, but that's a small price to pay if you're in need of a way to stop these two beasts. I should also note that it's possible to run Expert Belt (not Life Orb, the recoil kills you) and get similar results; Garchomp needs less HP/Def to survive Ice Shard, Tyranitar is still slaughtered by EQ, and min/min Heracross isn't always OHKO'd by Peck without SR/spikes support. Still, if you've got too many Choice users on your team already, Expert Belt is certainly usable.