By what morph, you mean wich combo ?

Well actually, EVERYTHING !

They are combos, so you can put fire in everything you want.

If you are asking wich combos have been created with fires, then it's something else.

Fire spider, Fire mojave and Fireflys are the one I know of.

There is also the fire spot nose I think.

So for, nothing really speacial. The Fire gene is really one that get every other combos or gene better. They just look nicer with it.