The Rear Fire Missile is a weapon that only appeared in Twisted Metal (1995). It functioned identically to the Fire Missile, but it shoots out from the rear of the vehicle, making it a good weapon to use when you're being chased. This would later be replaced with the "Rear Attack" Energy Attack in Twisted Metal 2 onwards. It was one of the four weapons from TM(1995) that was converted to Energy Attacks in TM2; the others three being the Drop Mines, the Freeze Missile, and Jump (catapult).
Since TM2, it's changed from firing a Fire Missile backwards to nearly any currently selected weapon. In Twisted Metal (2012), some weapons have an alternate fire/mode activated by pressing Down on the D-pad.