Toxic Sweeping Mightyena
Suggested item: Toxic Orb
Suggested ability:Quick feet
Crunch/sucker punch-Crunch offers STAB and might lower defense. Sucker punch comes up should a pokemon have a priority move. Crunch is more reliable though.
Facade-Gets boosted through the toxic orb.
Ice Fang/Thunder Fang/Fire Fang-Ice Fang is good to deal with Gligar, a major NU threat. Thunder deals with water and flying types, and fire for grass types.
Roar/taunt/yawn/Super fang/Rest-The first three are to force switches and preventing pokemon from trying to set up on mightyena, super fang is for wall breaking bulky pokemon. You could also consider using rest to shrug off any damage and status. Heal bell support would be recommended.
The idea with this set is to have the toxic orb activate Mightyena's ability, which boosts his speed when he has status. This also prevents him from being hit by status like Burn and paralysis, which would limit his sweeping abilities. Facade also gets stronger thanks to it. You could also use a choice band and hope the opponent carries a generic toxistaller or has toxic spikes to give you some status. This is more beneficial, but more situational.