Personally my favorite is Mega Aggron. I mean, first of all Aggron is my favorite Pokemon period, but he gets a mega, becomes pure steel type and has the Filter ability.
10 1/2 resistance
and thanks to filter, and the fact he only has one type which is steel, he only has 3 1.5 weaknesses (fire, fighting and ground).
Then again, his Sp. Def still isn't anything to boast about.
I GOT 'DEM HUMPS.
Doctress Who:You can be my Brony bitch ;D
Droctress Who:Jas, would you like me to make you a sandwich?
JesusChrist: Well if you insist Jasthn I'll use it with you. Spread them cheeks
Tragedy_and_Comedy: Jas is about as dangerous as a kitten.
Blood Lord:I hit your dog with mah truck. :3
Lenore Celestalis:*jumps on your back* weee~