h-e-r-m-i-o-n-e-deactivated2012:

Q: Why did Dumbledore want Ron to keep his deluminator?

A: Because he knew that Ron might need a little more guidance than the other two. Dumbledore understood Ron’s importance in the trio. He wasn’t the most skilled, or the most intelligent, but he held them together; his humor and his good heart were essential. —J.K.