Some of which are already technically illegal, its just a law that's not enforced well.
I suppose the big one I'm waiting for is electric motorbikes - I've whinged them on HN beforehand, but those buggers can be heard from blocks away, waking or annoying thousands - tens of thousands! - of people in built-up urban areas.
(ed. spelling)
I know they won't kill the tire/wind sounds, but if they break the mental association of loud == fast == cool for men, it could be a game changer.
No more ridiculously loud acceleration from 'modded' cars and bikes...
Also heavy trucks / buses under acceleration can be loud too, hopefully those'll go away as well.