Shroomisaur
Smogon's fantastical fun-guy.
Bisharp isn't weak to Fairy, so Gyarados is a great partner. Not to mention Bisharp has STAB Iron Head to smash Sylveon/Clefable/Azu, so resisting Fairy isn't a big concern.Gyarados doesn't resist Fairy.
Honestly, I'd say Crobat actually makes a really good partner for Bisharp.
Crobat would make a good partner based on his typing, and a fast Brave Bird to check Fighting-types which Bisharp despises. Keep in mind though that Defog users don't pair well with Bisharp. One of Bisharp's biggest selling points is his ability to threaten opposing Defoggers and keep your hazards up, so using Defog yourself would be a waste.
Due to the Steel-type nerf Bisharp doesn't need Low Kick as much, but it's definitely a solid option on Bisharp. It's most noteworthy for catching Lucario on the switch, but also for OHKOing Heatran after SR, taking out opposing Bisharp, and also being your only decent option against Mega Aggron. The trouble is how hard it is to give up one of Bisharp's other moves like SD or Sub for the extra coverage.Anyone else notice how handy low kick can be? One shotting unsuspecting Heatran is extremely satisfying. I feel as though it deserves some recognition.