A whale!

Sea urchin, or a three legged water-buffalo.

a tank...no, that is more suited for a rook. or a chariot....no, that is also still suited for a rook. How about a Huge walking Windows Vista Logo?

praying mantis

It wouldn't make sense to change the Knight from a horse since chess is medievel themed battle and the Knights traveled by horse. To change to for example a raging chess bull, you would have to change the name of the piece to either a bull fighter or even a bull rider like at a rodeo. I guess you and most everyone who responded to this and suggested their changes aren't much into tradition and want to change the way things are done. You all probably want a playoff in the major college football program instead of the BCS. Baseball is probably to slow a sport for you to follow. You probably crave more scoring in hockey. And you probably know nothing about soccer...

Did anyone say a monkey?, I always wanted a monkey!!

un manati!

Just when I think threads here cant get any sillier...  they do !!

I've always wanted to see a bakery themed chess set. ... Croissant to b3, check!

Nah, I've seen sillier than this. This barley scratches the surface, of some topics.

If you mate the croissant with jelly, would that be "Smothered Mate".

TY, TY,.. try the veal.

maybe "Smucker's Mate"?

A bull

A centaur, possibly more brains than other animals

Nah, a chimpanzee has the most brain power.

a ninja. if it was a ninja, your opponent could still make 4 or 5 moves before he even realizes he lost the game already.  Ninjas are sneaky that way.

A springbock which can make 15 meters jump, and can thus expand the knight move to all the squares of the chessboard

I like also the jumps of the grasshopper!

This cat: http://uk.youtube.com/watch?v=muLIPWjks_M

Very knight like.

to a elephant, its also a piece in chinese chess.

That's easy.  I would change the Knight to Kday.

K silent in both, of course.