Volcarona would have to be my pick here, for sure.
To me, Volcarona's design seems to be very to-the-point, without being overly complex or anything of the like. This is the first bug-fire Pokémon we have ever gotten, and if we were to create a structure for it, I'm sure not many of us would have been able to do it any better, including myself. Its body color is grey, white, and orange, with its eyes being baby-blue; if you ask me, this is a very interesting combination!
If I were to choose more than one, then my second option would likely have been Munna. Although it's round in shape for most part, I believe it has a very complementing color-scheme; in my eyes, pink and purple seem to fit each other very well. Due to similar reasons, I also would have voted for Audino.