I don't listen to anything because it's too distracting. Some people say that classical music (no lyrics) helps them. If I'm in a coffeeshop or somewhere not very quiet, I'll listen to a white noise track on my phone.
The drag racers just outside my bedroom window. They provide the most obnoxious sounds that nothing would be able to trump that on test day. If I need to escape them, then I would go to the library or nearby coffeeshop!