First there was the Jesus fish, in its various forms.
<JESUS><

As a symbol of pride on the back of a car, it evoked about as much respect as My child is an honor student.

Then along came the Darwin fish

<DARWIN><
 _| _|   

Growing up in Northern California, I bore witness to more of the latter.

Now this is where it gets interesting. Just the other day I saw a new spin on the whole car-fish thing:

\  /^^^^^\          
 >< TRUTH< <DARWIN><
/  \_____/  _| _|   

See, the big fish (marked TRUTH) is eating the little fish with legs (marked DARWIN). Apparently this symbolizes that anyone who knows the truth of creation can overcome the filthy lies of the late Mr. Darwin and his ilk.

Of course, I find it hard to deny the evolution of species by means of natural selection while still acknowledging that big fish eat little fish.