Hello there! First post incoming.
Now, I will preface by saying that I've never been much of a competitive battler. however, all the new changes and additions with gen VI has me very intrigued. As someone that's always liked banette despite his failings, the introduction of his mega evolution is something I've been pouring my brain over.
My thoughts:
Megabanette has OU potential, the cornerstone of which being the fact that it can counter megagengar, which, barring bans, has a very good chance of being one of the more used megas. With high attack and a stab, SE priority move, it is perfectly poised to hit gengar's weakspots, who lacks both strong defenses and priority of it's own. This gengar lock is further cemented by banette's overlooked access to pursuit, which can be included with destiny bond through breeding. Though I lack the knowledge to do straight calculations, and will be requesting here, it seems highly likely that megabanette *can* OHKO on gengar, shutting the shadow pokemon down before becoming megagengar. I acknowledge there are other cases to look at where things aren't so clean, and will be making requests following this.
Another key point, as noted earlier in this thread, is priority destiny bond. This is something which is very powerful, as it can ensure banette will at least trade evenly, up to and including with the opponent's mega. banette's forth move is most likely best served with your choice of priority status, or taunt, depending on your team/meta needs.
Nature: Jolly/Adamant
EVs: 4 HP/252 Atk/252 Speed
Hold: Banettite
Moveset:
-Shadow Sneak
-Pursuit
-Destiny Bond
-Will-O-Wisp/Thunder Wave/Taunt
More thoughts
1) The EV SPREAD:
-While slightly counter-intuitive, the purpose of this set is due to the fact that banette speed-ties with scizor. For this set, banette's key weakness is enemy priority, and bullet punch is one of the main ones to contend with. If meta changes and speedy scizor fades out, then evs might see adjustment, as this is a set that would otherwise be able to ignore speed thanks to prankster+priority. Otherwise, you probably still the need the speed.
2) shadow sneak seems like a staple move for banette. Reliable, priority stab, which allows you to turn on your mega evo on command.
-With this first point, I would like to request some damage calculations of Megabanette shadow sneak vs:
--Gengar (result is most likely obvious, but for the sake of not taking anything for granted)
--Megagengar (For circumstances where Megabanette is coming in after megagengar gets off the ground)
--Starmie (constant OU favorite. Megabanette has type advantage, and star doesn't have priority, but Banette most likely can't survive starmie's special hits. does spinblock still however)
--Scizor (Bullet punch is going to be the most played priority move that can hit banette, and Scizor is the most played user of bullet punch. Scizor has lost ghost resistance, so while still bulky, it will take more damage. question is: how much?)
--Azumarill (The other main priority move that can hit Banette, with the pokemon that will be most likely to use it. I don't see this one being as big of a deal due to WoW however)
If there are any other major ones worth noting, feel free to contribute!
3) Pursuit exists as part of the one-two punch with shadow sneak to drop gengar. Prediction is required, yes, but it's not a bad move in general to hit switches with megabanette's high attack and steel no longer resisting dark. gives you an option for hitting normal types as well. Also has excellent synergy with destiny bond, not only due to causing switch pressure, but can allow you better control over when you take your turn, manipulating how long your bond lasts.
-Any damage calcs that anyone would be interested in contributing with pursuit would be greatly appreciated!
4) Priority Destiny Bond via prankster is very nasty. it's habit of forcing switches combos well with pursuit, creating another nasty kind of lock for the enemy. It ensures that megabanette has a high chance of at taking at least one enemy with it, making it one of the best moves for this slot.
5) This slot is flexible for your team's needs/in light of the meta. Right now my thoughts tend towards will-o-wisp for it's chip damage and cripple on physical attackers, but paralysis can make life tough for fragile speedsters, and taunt can prevent mons from trying to set up on Megabanette.
In conclusion, Megabanette, while maybe not as flashy as some other megas, certainly has potential depending on how the meta falls into place in the future. And really, if you can use this haunted doll to cripple one of your opponent's mons, and take out either their mega or two of their mons, you can give banette a pat on the head for a job well done.
So, that's that! Thoughts and data are greatly appreciated.