For those who said a mule can't reproduce, they can. It is VERY rare, though. Recently one was born in Colorado (I think? I don't really remember all of it).
A mule is a mare and a jack.
and because I feel unoriginal and too lazy to name an actually serious answer, I will say a mammoth.
Originally posted by talzamir Geldings don't breed much. Naming one.. hm. Bamboo Harvester (better known as Mister Ed the talking horse), or Cloud Ten or White Pharaoh (both better known as Silver, the Lone Ranger's horse).