Ability: Defiant
Nature: Adamant
Evs: 252 Atk/132 Spe/ 124 HP
Item: Lum Berry/Air Balloon
Moveset:
Swords Dance
Sucker Punch
Iron Head
Knock Off
That's the set I've been using on PO. Speed EVs allow him to outspeed uninvested Rotom-W's, and Lum Berry works surprisingly well with Bisharp. You can use Life Orb or Lefties in place of Lum Berry, but Life Orb recoil is annoying for a pokemon that needs to take a few hits and Leftovers isn't all to important. Dread Plate is a cool item, but Lum Berry allows Bisharp to continue its sweep with no fear of status.
Another good item is Air Balloon which allows Bisharp to set up on the likes of Gliscor, Excadrill, etc. However, this means that if Sticky Web is up, Bisharp isn't going to get an extra +2, which, in many cases, is very crucial. It's all up to preference really, but Lum Berry and Air Balloon are what I find to be the two best choices as they allow Bisharp to set up and demolish unprepared teams.
On a side note, Aegislash, Mega Khan, and physical Mega Luc are great partners for Bisharp, as one of them will often be able to sweep once the others have wreaked havoc on the opponent's team.