Camerupt @ Cameruptite
Ability: Magma Armor
Shiny: Yes
EVs: 216 HP / 168 SpA / 124 Spe
Modest Nature
- Fire Blast
- Earth Power
- Rock Slide
- Substitute
Not sure if it's been talked about it here yet, but Mega-Camerupt is super fun right now. Obviously it's not the easiest Mega to work/build around, but I've been mildly successful with it and have heard good things from others as well. It's also seen some WCoP play as well. M-Camerupt eviscerates balance defensive mons like Tang, Pex, Steela, etc. even without max special attack (though you can run it that way if you're not concerned with outspeeding Toxapex).
The key is bringing it on doubles or through VoltTurn, especially on opponent switches, against mons it's supposed to check/knock out. The good news? Those mons it beats are common threats in the meta and are often checks/switch-ins for some prominent mons that you might want on your team. For example, I'm running M-Rupt with Koko and Protean Greninja. So if I have my Koko in, I can U-Turn on say a predicted Tang switch. Mega-Camerupt now comes in. Or with Gren, I can go into Camerupt on a predicted Steela/Pex switch-in. Camerupt is also a solid check to most Magearna and Koko sets as well.
So why the moves I have provided? Fire Blast and Earth Power absolutely rip through opponents with their Sheer Force boost and M-Rupt's insane 145 special attack stat, even without being maxed out. Standard defensive M-Venu is 2HKO'd by Fire Blast even without Rocks for example. Standard defensive Fini is 2HKO'd by EP. Rock Slide is on my set over Ancientpower in order to guaranteed OHKO Volcarona, as the latter doesn't OHKO after a Quiver Dance boost. The name of the game though is Sub. Unless you're confident of the opponent's switch, I recommend always subbing with Camerupt. This way you can scout, and fire off a big hit on their Camerupt switch-in of choice. Some teams might not even have one, they may just hope they read the attack right and force you out with speed. This means that later on, their check might not even be able to check anymore.
There are also a plethora of options and variations you can make depending on your team make-up. You could put Rocks on over Sub to make Camerupt a hazard-setter in addition to a wallbreaker. Maybe you have Bulu or Koko and go with Nature Power, which provides Camerupt with Sheer Force boosted Energy Ball or Thunderbolt respectively. Ancientpower helps more against Pelipper, Gyarados, and Mence if those are causing you problems. Hidden Power Ice rips through Zygarde, Garchomp, and Lando-T if those are unfavorable for your team (though Fire Blast already min rolls at 99% on offensive Lando-T's).
Obviously it is rippy-dippy to Dugtrio unless you've got a Sub still up and Sash is either gone or not there to begin with.
tl;dr- M-Camerupt is a niche Mega pick that nevertheless synergizes extremely well with top Meta mons, like Koko and Gren, being able to beat threats such as Tang, Steela, Pex, M-Venu, Koko, and Magearna; it is also extremely versatile in its options/movepool.