Ideal Pet System:
Dungeon Siege-like, you can get - free it in a mission from a dungeon - or purchase one and feed it and watch it grow. It levels up by getting XP from battles, also you can feed magic items to your pet to make it stronger. Your pet gets more and more dangerous, until the end, when in the final battle you have a super powerful pet.
It was major fun watching a baby pet eating up magic rings and other magical items and watch it grow. The baby pet 3D models were super cute.