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Mega Hitmonchan
Fighting
Ability: Steel Fists (Iron Fists, except instead of a 20% boost, it's a 30% boost)
HP
>50 -> 50
Attack
>105 -> 145
Defense
>79 -> 100
Special Attack
>35 -> 44
Special Defense
>110 -> 102
Speed
>76 -> 114
Base attack is raised that high to make the mega worth it over a life orb, which will boost Hitmonchan's attacks more if the mega had less than base 140 attack. The mega is specifically designed to make it a nuisance to 'mons that are week to Mach/Bullet Punch.
Could also be run as a tank with Drain Punch boosted so high that a single hit against M-Aggron would restore Hitmonchan's health up to full. Then again, you can't ever bring it out against a Psychic/Fairy/Flying type.