Unsurprisingly, this thread is full of people who genuinely think M-Blastoise wouldn't be good with Shell Smash. Let's take a look at the facts:
>79/120/115 bulk
>Outspeeds the entire unboosted OU after one Shell Smash
>Only two weaknesses, both of which are fairly uncommon and have no priority moves
>Insane coverage including Water Pulse, Dark Pulse, Dragon Pulse, Aura Sphere, Ice Beam, and Flash Cannon along with an Ability that gives the four first moves a free Choice Specs boost
After a Shell Smash boost we'd be talking about a special attacker that can 2HKO Chansey after hazards, which is batshit insane considering that Chansey is supposed to be a full stop to all special attackers.
>+2 252+ SpA Mega Launcher Mega Blastoise Aura Sphere vs. 4 HP / 252 SpD Eviolite Chansey: 302-356 (47 - 55.4%) -- guaranteed 2HKO after Stealth Rock
There's hardly anything in A-S rank of OU that could even check this thing as Blastoise would simply OHKO all offensive Pokemon even with neutral hits.
>+2 252+ SpA Mega Launcher Mega Blastoise Aura Sphere vs. 0 HP / 4 SpD Keldeo: 321-378 (99.3 - 117%) -- 93.8% chance to OHKO
Yeah, hopefully you're carrying something with good amounts of special bulk that isn't weak to Water, Ice, Fighting, Dark, Dragon, or Steel, and is capable of outspeeding this thing at +2 Speed and also has the power to smash through its bulk. You'd think that specially defensive Unaware Clefable solves your problems, but since it would also ignore Blastoise's Def/SpD drops, it couldn't actually do anything back and would hopelessly get 3HKO'd by Flash Cannon while it attempts a 4HKO with Moonblast.
tl;dr Saying that Shell Smash M-Blastoise would be anywhere below OU is absolutely retarded and the only people who think that are the same people who thought M-Metagross and M-Sableye would both be shit and BL at most.
