The sound of a Saturn V rocket, full volume. That’ll keep people from bothering me ! And when I’m an grumpy old guy, it’ll keep those kids off my lawn too !
The sound of one hand clapping would be a pretty neat trick.
I know a fellow who can do a very good vocal impression of the call of a female moose in heat.
This caused him a bit of a problem while canoeing, when a male moose swam after him for the best part of a day, quite exhausing him and his paddling partner from the marathon chase.
A full orchestra. If that counts as more than one sound, a violin. That way I can actually make my own music. Of course, being able to tell pitch would help with that too…