Let's face it. Superspeedy Mega Metagross is going to be overpowered. It is going to wreck whole teams in the rating battle. There are quite a few Hoenn pokemon that deserve mega evolutions. Why did Metagross get one?

What are his stats? And what is his ability?

I don't know his stats, but he gets Tough Claws.

Metagross was in OU back in Gen V, but the nerfs to Steel type in Gen VI (no longer resists ghost or dark) means that it's now in UU. Metagross is a Pokemon that probably needs a Mega to stay competitively viable

Perhaps, but I feel like the Speed Boost and Tough Claws will make this one a force to be reckoned with. Other Pokemon in UU could also deserve Mega Evolutions.

but 

what about pokemon that acctually need a mega?? LIke for example dunsparce and torkoal

I wanted Mega Dunsparce a bunch, but we won't be seeing it in a Hoenn game - Mega Torkoal I would definitely like to see, however (as well as something that could make Spinda a viable Pokemon! :D)

Ooh! Like a Mega Spinda with an Attack and Speed boost with Dizzy punch! Something like that would be really cool.

Well I doubt his speed base stat would increase over 10 points, if at all...Mega would likely mostly affect Atk, Def and Sp. Def so I don't see why he would be any better than a lot of the current mega pokemon

PS: I don't think Mega would be very usefull for a pokemon like Dunsparce.  Even a 100 point boost would only give him 515 in his stats which would make him useless as a mega. Torkoal is in a similar boat, although not quite as bad...just not very interesting.

I do, but only because my vision of Mega Evolutions is very different than Game Freak's, and that's a topic for another day.