Wow, this is exciting, there are so many good ones already. As soon as it became clear that Flying/Fighting would win I started work on a paratrooper concept (it seems I was ninja'd by WPS!). Here's my WIP:
Why a paratrooper? What better captures the idea of a momentum swing than the guys that bust down your front door when you think you're safe on your home turf? Besides, nothing says secondary Fighting type like the guys that jump straight into enemy territory.
A few design notes here: I generally dislike Pokemon with blatantly human props, so I should note that the "helmet" is some sort of bony forehead, while the "backpack" is just a hunchback, even though the perspective makes it look like a separate element. On the same note, I tried to imply that the parachute is a fused set of wing-hand-things. Also, this is supposed to be a simian sort of fellow. The jagged lines (where color transitions will go) are supposed to be fuzzy, the feet have opposable thumbs, and I like the idea that the backpack and "strap" coloration is silver/white, as in a silverback gorilla. As for the rest of the colors, I'm thinking a sky-blue body and beige or black hand-wing-things.
Constructive criticism is very welcome.