Aerial Ace Barbaracle
Barbaracle @ (whatever you want, but I really like Life Orb)
Ability: Tough Claws
EVs: 252 Atk / 4 Def / 252 Spe
Naughty Nature
- Shell Smash
- Aerial Ace
- Liquidation
- Stone Edge
+2 252 Atk Tough Claws Barbaracle Aerial Ace vs. 252 HP / 252+ Def Chesnaught: 368-436 (96.8 - 114.7%) -- 81.3% chance to OHKO
Normally, Barbaracle can't get past Chesnaught (because it resists both of Water/Rock STAB combination), but the addition of Aerial Ace changes this completely. It also allows Barbaracle to get past bulky Grass-type pokemons such as Tangela, Vileplume, Gourgeist, and Lilligant. Ice Beam would be perfect...if only it was a physical move.
P.S. You could think that a STAB Stone Edge is better than Aerial Ace, until you take in account the different accuracy.
+2 252 Atk Life Orb Tough Claws Barbaracle Aerial Ace vs. 252 HP / 184 Def Amoonguss: 406-478 (93.9 - 110.6%) -- 62.5% chance to OHKO after Black Sludge recovery
+2 252 Atk Life Orb Tough Claws Barbaracle Aerial Ace vs. 252 HP / 252+ Def Eviolite Tangela: 166-198 (49.7 - 59.2%) -- 99.6% chance to 2HKO (you have a higher chance to 2HKO this thing and with 100% accuracy, unlike with Stone Edge)
+2 252 Atk Life Orb Tough Claws Barbaracle Aerial Ace vs. 252 HP / 252+ Def Vileplume: 307-361 (86.7 - 101.9%) -- 18.8% chance to OHKO after Black Sludge recovery