And the winner is.....
BRENT NEWHALL with the following entry:
Play intelligent weasels with other beasts in forest. 13 points in Sneaky, Vicious, Persuade, Health. Beat 1d6 to succeed; 1 damage per hit
I chose this because, let's face it, playing an intelligent weasel? Who doesn't want to do that? The system is simple and usable and it even has as a damage system. You'd probably have to adjust things depending on the size of the animal but hey - there's only 140 characters to play with! Well done, Brent, a copy of my SKETCH game The League Of Seven is on it's way to you now.
A special mention goes to Allon Mureinik with this entry:
Dragon souls hiding in cat bodies. Divide 10 points between attributes: flight, fire-breath, magic. D10+Attribute vs. difficulty to succeed
Mainly because of the concept - the souls of dragons inside the bodies of cats? That's just cool on toast.
Thanks to all of you who entered!