I dunno, bored now, so I felt like starting a Pokemon thread because I am a gigantic nerd. And I like people's opinions. So, here we go...
Usefulness in Battle: Salamence
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Probably the single most effective and powerful (non-legendary) I have ever raised.
Appearance: Milotic
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This Pokemon basically captivates the minds of all Trainers. The difficulty that you have to go through to get it more than pays off when Feebas finally evolves, in battle and out.
Intimidation: Mewtwo
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Is there any real doubt for this one? Any time you battle someone, and they toss out a Mewtwo, no matter who you have, everybody thinks the same thing: Oh, shit.
Most Annoying: Zubat
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Complain about Magikarp or whatever all you want, but nothing is more annoying than seeing a billion of these in a cave that you are lost in, especially with their Supersonic.
Most Badass: Cubone
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Think about it: he wears the skull of his deceased mother, implying that he mutilates her flesh and rips off her skull.
Can't really think of any other categories right now...what about you?