Shuckle @ Mental Herb  
Ability: Sturdy  
EVs: 248 HP / 252 Def / 8 SpD  
Relaxed Nature  
IVs: 0 Atk  
- Sticky Web  
- Stealth Rock  
- Infestation / Knock Off / Toxic
- Encore

Other Move Options: Final Gambit, Rock Tomb
Notes: Shuckle is one of the few pokemon that can set up Sticky Webs and Stealth Rocks, making it a huge asset to hyper offensive teams. With Sturdy and Mental Herb, it will always set up at least one of its hazard options against opponents packing Taunt or powerful moves.
Infestation allows Shuckle to trap foes locked into a move, chip them, and safely set up hazards or switch into a wall breaking partner. Knock off removes Eviolite from magic bounce users like Natu while crippling opponents who may capitalize on Shuckle's passive nature. Toxic is Shuckle's best way to inflict damage against opposing defoggers and rapid spinners but leaves it set up fodder for Poison / Steel types, Magic Guard users, and Guts users.
Encore prevents Shuckle from being fodder for set up sweepers.