The ideal "fuck you, parents" present must be noisy, and yet must require no batteries. Drums & cymbals are a good choice, as is a vuvuzela or an Aztec death whistle.
the absolute best fuck you present is no present at all, there is nothing parents like more than kids that have nothing to do
A vuvuzela is mean. I'm not even related to you (I think), and I want to disown you for that suggestion.