My favorite, an absolute wall for both thundy, landy, and heatran. Storm drain is a great wall to the ever popular politoed, milotic and suicune.
Gastrodon @ Expert Belt
Ability: Storm Drain
Level: 50
EVs: 180 HP / 108 Def / 216 SpA / 4 SpD
Quiet Nature
IVs: 0 Spe / 0 Atk
- Earth Power
- Scald
- Ice beam
- Protect
offensive
216+ SpA Expert Belt Gastrodon Ice Beam vs. 0 HP / 0 SpD Landorus-T: 480-566 (150.4 - 177.4%) -- guaranteed OHKO
216+ SpA Expert Belt Gastrodon Ice Beam vs. 0 HP / 0 SpD Thundurus: 240-283 (80.2 - 94.6%) -- guaranteed 2HKO
216+ SpA Expert Belt Gastrodon Earth Power vs. 180 HP / 0 SpD Shuca Berry Heatran: 283-334 (76.9 - 90.7%) -- guaranteed 2HKO
216+ SpA Expert Belt Gastrodon Ice Beam vs. 252 HP / 252 SpD Mega Salamence: 336-398 (85.2 - 101%) -- 12.5% chance to OHKO
216+ SpA Expert Belt Gastrodon Earth Power vs. 252 HP / 252+ SpD Aegislash-Shield: 161-190 (49.6 - 58.6%) -- 60.9% chance to 2HKO after Leftovers recovery
defensive
252 Atk Parental Bond Mega Kangaskhan Return vs. 180 HP / 108 Def Gastrodon: 289-342 (70.8 - 83.8%) -- guaranteed 2HKO
Gastro's bulk gives it good survivability, and storm drain gives potentially recovery if paired with surf. Can OHKO most VGC threats if running offence, however if against a more (unusual) defensive set [e.g max HP/SpD M-salamence, Shuca-Tran, Max HP/SpD shield aegi] it can still pick up the 2HKO. Its abysmal speed also gives it fantastic potential in trick room.
Gastrodon @ Expert Belt
Ability: Storm Drain
Level: 50
EVs: 180 HP / 108 Def / 216 SpA / 4 SpD
Quiet Nature
IVs: 0 Spe / 0 Atk
- Earth Power
- Scald
- Ice beam
- Protect
offensive
216+ SpA Expert Belt Gastrodon Ice Beam vs. 0 HP / 0 SpD Landorus-T: 480-566 (150.4 - 177.4%) -- guaranteed OHKO
216+ SpA Expert Belt Gastrodon Ice Beam vs. 0 HP / 0 SpD Thundurus: 240-283 (80.2 - 94.6%) -- guaranteed 2HKO
216+ SpA Expert Belt Gastrodon Earth Power vs. 180 HP / 0 SpD Shuca Berry Heatran: 283-334 (76.9 - 90.7%) -- guaranteed 2HKO
216+ SpA Expert Belt Gastrodon Ice Beam vs. 252 HP / 252 SpD Mega Salamence: 336-398 (85.2 - 101%) -- 12.5% chance to OHKO
216+ SpA Expert Belt Gastrodon Earth Power vs. 252 HP / 252+ SpD Aegislash-Shield: 161-190 (49.6 - 58.6%) -- 60.9% chance to 2HKO after Leftovers recovery
defensive
252 Atk Parental Bond Mega Kangaskhan Return vs. 180 HP / 108 Def Gastrodon: 289-342 (70.8 - 83.8%) -- guaranteed 2HKO
Gastro's bulk gives it good survivability, and storm drain gives potentially recovery if paired with surf. Can OHKO most VGC threats if running offence, however if against a more (unusual) defensive set [e.g max HP/SpD M-salamence, Shuca-Tran, Max HP/SpD shield aegi] it can still pick up the 2HKO. Its abysmal speed also gives it fantastic potential in trick room.