Staraptor. This Pokemon is just a beast with decent stats, moves and abilities that increase your own attack or decreases your enemy's attack. All this, and he's one of the first Pokemon you can catch. He was the first Pokemon other than my starter that I kept all the way to Post Elite Four.
What I hate is how people like Gen 5 designs violently defend it and accuse anyone of not liking it as genwunners. This is despite the fact that my favorite designs of Pokemon come from 4 and 3. 5 just seems like the designers didn't seem to try and picked up Pokemon they literally right in front of them like furniture, gears and a ice cream cone. Not to mention that these designs seem to be trying to attract kids mostly despite being so weird and out of place.