You, the user
Your city and/or internet service provider.
Your home address and phone.
Your physical location within about 4 feet.
IP addresses cannot be tracked.
A local area network
A domain controller
To play jokes on people.
To do charitable deeds.
To get counseling.
To report a crime.
Issue a subpoena for the proxy's log files.
Call up the police where the suspect lives.
Violate the suspect's Fifth Amendment rights.
Search for the suspect using Google Transparency Services.
American Civil Liberties Union
Here's an interesting quiz for you.