Choiced Rotom-W (Rotom-Wash) @ Choice Scarf / Choice Specs 
Ability: Levitate  
Level: 50  
EVs: 252 SpA / 4 SpD / 252 Spe  
Modest Nature  
IVs: 0 Atk  
- Hydro Pump  
- Volt Switch  
- Thunderbolt  
- Trick
Choice Specs Rotom can run bulky with 236 hp/252 spa/20 speed, speed for speed creeping bulkier finis. 
Defensive Rotom-W (Rotom-Wash) @ Iapapa Berry  
Ability: Levitate  
Level: 50  
EVs: 252 HP / 236 Def / 20 Spe  
Bold Nature  
IVs: 0 Atk  
- Volt Switch  
- Hydro Pump  
- Hidden Power [Ice]  
- Toxic / Thunder Wave / Will-o-Wisp
Standard Defensive Rotom-W for dealing with mega salamence whilst keeping pressure on hippo. Last move can be a variety of moves.

Water-Z Offensive (Rotom-Wash) @ Waterium Z  
Ability: Levitate  
Level: 50  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Hydro Pump  
- Thunderbolt  
- Volt Switch  
- Hidden Power [Ice]
The standard offensive spread, max speed for outspeeding Mimikyu, rest in spa for hardest hitting water-zs.

Other options for Rotom-W include electroweb, where speed is generally at 128 for greninja. Assault vest and dual screens rotom are seen very very seldomly.