I have no problem with people making minor mods on their exhaust systems to give the car a little bit of a "throaty growl", but some people think that if a little is good, then a LOT must better and turn their cars into a complete nuisance. No, junior, just because you can put a coffee-can, loud exhaust on your Civic, it doesn't turn it into a Ferrari FXXK. I'd like to see them crack down on motorcycles, too, especially Harleys and other "if it's slow, at least I'll make it noisy" types.
I'd love to see them ban leaf blowers where I live in suburban Chicago. More of a noise menace than all of the loud cars around here, combined.