I've been using Yawngonaut to some success. Wreaks all sorts of havoc and forces switches like you wouldn't believe.
Arghonaut @ Leftovers
252 HP/96 Atk/160 Def
Adamant (+Atk, -SA)
~ Focus Punch
~ Recover
~ Yawn
~ Waterfall
Basically when a counter switches in they have to deal with Yawn. Using Arghonauts resists and Yawn to set up opportunities, you can focus more on bulk and blow things away with Focus Punch. I need more testing, and maybe some EV tweaking, but thus far it's solid.
Arghonaut @ Leftovers
252 HP/96 Atk/160 Def
Adamant (+Atk, -SA)
~ Focus Punch
~ Recover
~ Yawn
~ Waterfall
Basically when a counter switches in they have to deal with Yawn. Using Arghonauts resists and Yawn to set up opportunities, you can focus more on bulk and blow things away with Focus Punch. I need more testing, and maybe some EV tweaking, but thus far it's solid.