Well, i'm sure weve come across pokemon or pokedex entry that you found was cool, creepy, scary, weird, or just plain wrong. Here you can tell about the one pokemon that you admire, creeped you out, or one you wouldnt like to run into in a dark ally, that just happend to catch your eye. Remember to think about the anime as well, not only the games.
Off the top of my head the first Poke that comes to mind is chandelure. It steals and burns the souls of its victoms as fuel for its fire.....if thats not creepy I dunno what is.
One I think is really cool is Slowking. Intelligence rivaling award winning scientists is purtty cool, and being able to speak english always a plus. Makes me wonder how far I could get in a chess match.
I found the Bisharp evolution line to be very interesting, due to them being the first Bipedal-styled Pokemon that work as a vicious murder-gang.
Especially the Pokedex entry on White, which describes that the Pawniard will work hard to bring down a foe, and allow Bisharp to deliver the final blow.