Rillaboom @ Assault Vest  
Ability: Grassy Surge  
Level: 50  
EVs: 252 HP / 116 Atk / 60 Def / 76 SpD / 4 Spe  
Adamant Nature  
IVs: 0 SpA  
- Wood Hammer  
- Grassy Glide  
- U-turn  
- Fake Out

Unown
Move options:
- offensive: High Horsepower, Superpower, Darkest Lariat, Knock Off
- supportive: Drum Beating

Unown
Offensive calcs:
- 116+ Atk Rillaboom Grassy Glide vs. 0 HP / 4 Def Mega Golduck in Grassy Terrain: 152-182 (98 - 117.4%) -- 93.8% chance to OHKO
- -1 116+ Atk Rillaboom Wood Hammer vs. 0 HP / 0 Def Mega Walrein in Grassy Terrain: 188-224 (101.6 - 121%) -- guaranteed OHKO
- -1 116+ Atk Rillaboom Wood Hammer vs. 252 HP / 4 Def Slowking in Grassy Terrain: 204-242 (100.9 - 119.8%) -- guaranteed OHKO
Defensive calcs:
- +2 252 SpA Fairy Aura Mega Meowstic Moonblast vs. 252 HP / 76 SpD Assault Vest Rillaboom: 175-207 (84.5 - 100%) -- 6.3% chance to OHKO
- 252+ Atk Glastrier Icicle Crash vs. 252 HP / 60 Def Rillaboom: 176-210 (85 - 101.4%) -- 6.3% chance to OHKO
- 252 SpA Mega Charizard-Y Heat Wave vs. 252 HP / 76 SpD Assault Vest Rillaboom in Sun: 168-200 (81.1 - 96.6%) -- guaranteed 2HKO after Grassy Terrain recovery

Rillaboom @ Choice Band  
Ability: Grassy Surge  
Level: 50  
EVs: 252 HP / 196 Atk / 60 Def  
Adamant Nature  
IVs: 0 SpA  
- Wood Hammer  
- Grassy Glide  
- U-turn  
- High Horsepower

Unown
Move options:
- offensive: High Horsepower, Superpower, Darkest Lariat, Knock Off

Unown
Offensive calcs:
- 196+ Atk Choice Band Rillaboom Grassy Glide vs. 252 HP / 180 Def Mega Slowking in Grassy Terrain: 236-278 (116.8 - 137.6%) -- guaranteed OHKO
- 196+ Atk Choice Band Rillaboom Grassy Glide vs. 0 HP / 0 Def Urshifu-Rapid Strike in Grassy Terrain: 240-284 (137.1 - 162.2%) -- guaranteed OHKO
Defensive calcs:
- 252+ Atk Glastrier Icicle Crash vs. 252 HP / 60 Def Rillaboom: 176-210 (85 - 101.4%) -- 6.3% chance to OHKO