Mega Charizard X

Kangaskhan - the baby comes out and fights.

Hmmm...I haven't really used the mega evolutions much, but I think I'd have to say Mega Absol.

Mega Tyranitar

 

Just look at that battle stance... She's going to wreck the shit out of you look.

Mega Houndoom is metal as firetruck. Probably the best looking mega evolution, and I wish it could've been a full 3rd evolution stage, design-wise anyway.

I think Torkoal should have got a mega

Mega Blastoise is pretty cool even if I quit the game like right after I started using mega evolutions shhh

Mega Lucario

 

That's by far my favorite Mega evolution because it looks so badass and the STAB bonus of Adabtability can destroy team ^_^

 

Also,Mega Mewtwo Y,Mega Charizard X,Mega Mawile and Mega Tyranitar

 

Just look at it, you can't say it's not awesome

I'm going to go with Mega Blaziken. Mine has helped me out too many times to count in battles, I love the guy. Especially with Speed Boost, it's pretty dangerous.

 

 

Runner-up goes to Mega Garchomp, probably. Haven't used it, but I love Garchomp, and it's mega form looks pretty cool.

Mega Absol.