An almost ridiculously easy way to silence
a car alarm that does not involve being inherently evil
If you have a few burly friends with you, a very easy way to shut the offending alarm off is to simply lift the back end of the car off of the ground until the noise ceases. The car alarm thinks the automobile it's protecting is being towed away, and thankfully, alarms are made to shut off once this happy event occurs. And you don't have to get ticketed or arrested for lobbing bricks or otherwise hurting someone's poor car (though you can give the auto in question a nice hard drop on the ground, if you feel so inclined -- no pun intended).