Cat Summoner
What is the feasibility/playability of a Summoner who only summoned cats? I bet you could find different strength cats in various monster books to equate to every summoning spell: House cats, lynx, bobcat, cougar, cheetah, jaguar, leopard, lion, tiger, sabertooth, etc.
I think it would be fun, but I'm a big cat fan (that is, a fan of cats larger than house cats).