My favorite is Reshiram because I find it adorable and it has a very unique, original design. It is also very underrated, at least in my opinion.
Hydreigon probably comes in second. When I first saw Deino, I was basically thinking "Hmm, what is this? Maybe I should catch and train it.". I found its evolutions rather surprising, but when I saw Ghetsis' Hydreigon, I knew immediately that that was what it evolved into. I found its appearance hilarious for some reason, too.
Four Shinies now! Zara (Audino, female) (10/24/12), Kiki (Ledian, female) (10/16/13), Ivy (Carnivine, female) (10/31/13), Hoshi (Relicanth, male) (11/16/13)
Friend Safari: Rock (Dwebble, Onix, and Shuckle)
3DS FC: 2380-2837-4651 Name: Hy6507
I have officially claimed Chespin!
Current hunt: Chespin (MM) 200 eggs!