I've actually seen someone do the thing many of us wish we could do, and start ramming the cars ahead and behind because he got boxed in like this. His bumpers were fucked all to hell but he got out, put the big pieces in his trunk, and drove off.
No idea what was going on but he was clearly having a bad day.
Personally if I WERE to do this, which of course I NEVER would, I prefer to use a bottle jack to lift the curbside corner up, then push from street side, making the car fall and skew to one side, giving me more room to exit. Note: also works on assholes parking across multiple spaces.
If you're ever in a parking garage, or somewhere with flat level surfaces, a bottle jack and wheel dollies could let you roll the entire car around.
People in Boston sometimes have large rubber bumper covers, because according to my uncle "it's apparently just a cultural norm to ram the other people's bumpers to figure out how large the parking spot is"