Blast the windows off.
Actually, that would be possible. Even at low volumes (volumes low enough to maintain some degree of hearing) the rear window starts to resonate. With a suitable tech-house track and volume pumped to the max it could be quite possible to blast it off. Along with your eardrums, eyeballs, and all sorts of fragile things within the car.
Of course, with the boot opened, it's mostly harmless, and there's nothing like demonstrating to your friends (and the entire neighbourhood within the kilometer) the power of bassdrum. Bonus points for driving to the beach and doing this there (sound waves travel awfully far over water, apparently). Special achievement awarded if it's late summer night at a summer cabin and you decide it's time for a rave (achievement requires you park your car as close to the shore as possible with the woofer facing the water).