If I've said it once, I've said it a thousand times.
Find your favorite guitar shredder, then ask him to play as fast as normally does, but do it left handed, better yet, at the same time.
Angelo can.
He plays a double neck guitar, not a standard double neck, a guitar that looks like a V, with one side being truely right handed, the other side being truely left handed, and he plays them at the same time. I've even seen a newer model that has 4 necks. That's amazing in itself.
Sometimes I hit notes only dogs can hear.