Musharna is my choice. Once you get rid of all opponent's dark type (if he has any), this thing is pratically unstoppable once she's setup a couple of CMs.
I'm referring to this particular set:
Musharna @ Leftovers
240 HP / 252 Def / 16 Spe
Bold Nature
Trait: Synchronize
-Calm Mind
-Moonlight
-Heal Bell
-Psychic/Stored Power
Her huge 116 HPs allow her to takes many physical attack, and once you start CMing you're basically protected even on the special side. A good partner for Musharna is Ninjask that can pass Speed Boost and that's why i slashed psychic with stored power, so you can even smash a lot more pokes if she can receives those boosts.
Adding to the insane bulk, a recover move in Moonlight (only nerfed with the rare weather) and the cleric move Heal Bell and you are basically covered by everything except crits (that always happen to me -.-).
The reasons that make me choose Musharna over others good mons is that Zangoose for me is too predictable and, if my opponent isn't a master of the guess, can be stalled pretty easly thanks to the common protect/subs and good physical threats or pokes with immunity to his attacks, not counting that he has pretty shitty defenses and his weak to 2/3 of hazards (even Musharna, but she can heal herself).
Braviary is a really good mon, but once you set up SR, you can start guessing wich set he's running. I'm not good at using him, but i've faced many and, for me, the CB set is the most scary (not that much). Already, you have to guessing right with Braviary's choice set and the BU set can be countered more easly once you understand that he has leftovers (yes, if he's running LO, you can bluff and that can be more tricky to fight, but still manageble with a good special sweeper or good rock blaster).