Impish (+Def - Sp.A) is good nature for Mamoswine, and Jolly is a good nature for Weavile (+Speed - Sp.A).
Mamoswine has 110 HP / 130 Atk / 80 Def / 70 Sp.A / 60 Sp.D / 80 Speed.
Weavile has 70 HP / 120 Atk / 65 Defense / 45 Sp.A / 85 Sp.D / 125 Speed.
Mamoswine (M) @ Choice Band
Trait: Thick Fat
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Ice Shard
- Stone Edge
- Earthquake
- Icicle Spear/Crash
Weavile (F) @ Iron Ball
Trait: Pickpocket
EVs: 80 HP / 252 Atk / 4 SDef / 172 Spd
Adamant Nature (+Atk, -SAtk)
- Ice Shard
- Brick Break
- Fling
- Fake Out / Taunt / Thief
With Iron Ball, Fling is the most powerful move Weavile has access to (130 Power + STAB)
If you want to remain with the natures (Impish and Jolly), use the following EVs above.
Mamoswine with Choice Band and a Priority Move is a good choice. Weavile has more Speed and Sp.Def and 130 Power + Stab move.
Also in your team, you don't have any Dark or Ground Types, and I like having Earthquake in my team, great power and covers many types.
The 2 Pokemons can learn Ice Shard was a priority move, both have great attack and stab from Ice Shard but Mamoswine with Choice Band and with the best attack stat, can destroy many things.
Mamoswine is in OU tier and Weavile in BL tier.
Hope this helps!
