The Teddy Bear is a secret weapon that can be found in Warrior Within.
This weapon is pretty weak with its attacks but it heals the Prince with each hit he delivers on his enemies. It is indestructible.
This secret weapon can be found in the Mechanical Tower while in the present, after obtaining the Scorpion Sword. This weapon can be found in the dead-end hallway of the mechanical pit, where the prince uses the Spike Beasts to blow up the barrier.