Can You Use A Yoyo in Zero Gravity?

Not properly. Gravity reliant tricks such as 'walking dog' would be tricky, and 'cat's cradle' would be impossible, but you could make the yoyo leave and return to your hand by flickering your wrist. What would be bizarre would be the fact that the yoyo could go up and down the string in anhy direction. It would move quite slowly, and whether it would spin is debatable. If it didn't, getting it to roll back up again would be tricky due to lack of tension in the string.