Noivern @ Flyinium Z
EVs: 252 SpA / 4 SpD / 252 Spe
IVs: 0 Atk
Noivern has amazing stallbreaking potential with Taunt + Roost and uses that to destroy a plethora of balance staples such as Mandibuzz, Registeel, Milotic lacking Ice Beam, and Gligar. Noivern's niche defensive typing lets it switch into Fire-, Bug-, and Grass-types like Ninetales, Golisopod, and Shaymin, and its impeccable Speed stat lets it reliably revenge kill wallbreakers like Salazzle and Virizion. Noivern forms a brilliant core with Rhyperior and Mega Blastoise, as it can switch into scary Grass-types for them, while Rhyperior + Mega Blastoise forms an excellent core on its own, providing Stealth Rock and amazing entry hazard removal in Rapid Spin. Even though it has alarming issues concerning its Stealth Rock weakness and lack of bulk, these don't stop it from being an up-and-coming force in RarelyUsed!
Some replays showcasing Noivern's capabilities (these replays might not follow the exact set above; there are many viable variations to the set such as Super Fang > Flamethrower, Leftovers or Life Orb > Flyinium Z, etc):