First off, Inferno from Hot Spot

Outback from Brawn

And in an unexcepted turn of events, Cindersaur from Slash (shame about the face)

At the risk of colouring the debate, I find the top two to be uninspired, and would have liked them to be the IDW versions of Pyro and Ironfist instead. More generally, there's plenty of red fire engines and offroad vehicles they could also have done, such as RID Prime, PCC Smoulder and even G1 Rollbar. Just for a bit of variation.
Link here.