Othello the Moor (for a black bull/steer) ...please note clever pun, and Shakespeare reference...
Leprechaun (for a mini cow painted green)
Aristotle (a thinking bull or steer)
Nijinski (a bovine that's either very graceful or very clumsy)
...if intending to eat, surname appropriately. Our first lot of Angus were called:
All off to market last May, I still miss Wills, he was almost as good as my horses.
Our current cattle (Friesian steers) are called Batman, Pythagoras, The Pirate, Sergeant Pepper, Tiny Tim, Spot, Stripe, Charlie, and Chevron, mostly after body markings. Sergeant Pepper has a love-heart shape on his head, Pythagoras a triangle, etc.