Item: Choice Scarf
Evs: 252 Sp Atk, 252 Speed, 4 Hp
I know this is a fairly standard set, but it seems to work for me. I've tested extensively on Showdown. I run a team with Sticky Web, and it's evs allow it to outspeed most sweepers, even with them having a speed boosting nature, minus a Scarf. I love the versatility in terms of how many types get hit hard by a base 145 Sp Atk. I chose Energy Ball over Hidden Power, to abuse the fact it can safely switch in on a ground type move, as long as the Pokemon using it, doesn't have Mold Breaker. It then gains the ability to hard switch out, or Volt Switch out, giving it great momentum building.
Contrary to other people's opinions, a Scarf is a viable option, with the right team support. A team with other hazard setters, and a Rapid Spin user, could provide a great balance.