All animals as big as Eddie or larger can be ridden. Hit a creature with a bolt 
of lightning to stun them. Then, get near them, and press Triangle. While riding 
them, press X to perform an attack specific to that creature. Raptor Elk and 
Tullusks are a couple examples of creatures with melee attacks, while the Laser 
Panther shoots lasers from its eyes. The large wooden horse creatures in the 
final map area (with large swinging axes for tails) can also be ridden.