I'm a fan of Tri-Delt's dolphin, AOPi's panda, and Chi Omega's owl.
OPhiA's mascot is Raggedy Ann, whom we call "Ophia" (pronounced oh-fee-uh). Which is cute, but...animals are much easier, both to buy stuff of and draw (it's awfully hard to draw one while chalking!).
In my local chapter, each family has its own mascot too, which makes buying gifts for littles easier. We have Theta Frogs (my family), Delta Ducks, Xi Tigers, Omega Ladybugs, and Rho Cows.