So, I've been thinking about Mega Mawile for a bit and I came up with this set.
Physical Revenge Killer Mawile
Ability: Intimidate (Huge Power)
Evs: 252 Hp/252 Attack/4 Def
Moves: Sucker Punch, Iron Head/potential Fairy physical attack, Fire Fang, Thunder Punch/Ice Punch
As a revenge killer, Mawile can take advantage of having Intimidate without risking taking any damage on entry aside from hazards. It can then Mega Evolve into Mega Mawile, boosting its Defensive stats and Attack so that it has a better shot at killing the opponent. With Intimidate AND a boosted defense stat, MegaMawile could have a field day revenge killing a lot of physical threats (though I could imagine bulkier pokemon could be problematic.) Additionally, having access to an already decent attack stat before Mega Evolving and Sucker Punch allows Mawile to pick off some weakened threats WITHOUT mega evolving (meaning that it could continue to abuse Intimidate on entry later.
This + Trick Room Support/Wish Support= uuuuurggggghhhhh >_< --- Pokemon Black fc-5243 1202 3802 Megaman Rj fc:2493 5945 5724 Yugioh 2010 4383 3896 9610 http://stevenjobs101.wordpress.com/<---visit my blog :u!
MegaMawile will likely need loads of support to sweep effectively. As of now, we know that its STABs are walled by fire types, probably Steel types and several others. Most of its coverage moves being Dark type or rather weak(E-punches and fangs) doesn't help. Unless it's bulky enough to survive Magnezone's moves and OHKO back(IF it can), it's Maggy bait.
Of course all that are assumptions, since we don't know
a. how powerful Huge Power Mawile will be b. how bulky it will be after the mega boost
Trick Room support and maybe even bringing it in through Memento/Parting Remark is how I'd bring it into play once everything's dealt with, but the real work needs to be done before that.