Hyper Yo-Yo - Hyper Brain
Nowadays, there are many yo-yos that have plenty of spin just from dropping them and letting them dangle on the end of the string, but back in the day the learning curve for yo-yos was much steeper, making it tough to progress to more difficult tricks without first learning how to properly throw the yo-yo. Since the Brain will immediately return to your hand without sleeping if you don't throw it properly, this is a great trainer to get you to learn how to properly sleep a yo-yo.
If you are having trouble getting the yo-yo to return to you, check to make sure the string is wrapped around the axle three times. This goes for all auto-return models; if the string isn't properly wrapped three times around the transaxle, the auto-return function will not work. Always be sure to do this when changing strings!