Hmm, well like someone else said Fiji has the owl, SAE has the lion...Sigma Nu has the snake...they call their fall semiformal Snakes on the Lake...I always wanted to get invited so I could have a tshirt that said that haha.
I know Beta Theta Pi has the dragon, but I don't know if they consider it a mascot?
One of the Ag fraternities, Farmhouse or maybe AGR here uses the plow as a symbol/mascot thing. I am pretty sure it's AgRho though...
Other than that though I can't think of any other fraternities that have mascots, at least at my school anyway...maybe Jules knows of some others.