My favorites would have to be Hydriegon, Krookodile and Zoroark. Both Hydreigon and Krookodile are Awesome and powerful. As for Zoroark, it was one of the first B/W Pokemon I've known. I found it so cool and I've always told myself that I'll definitely get it on my team when I get the game (but up until now, I still haven't..) Scrafty's awesome too with great attack and defenses, but a tad slow. Makes a great Payback user. x)
Do I have o answer a question or something? Oh, which Dark-type's design do I not like? Hmm..that'll have to be Shiftry. It looks rather cranky and old lol.
And now it's time to update the list.