... like how about a new sound for MR sound systems: the sound of slack being taken up. Heard it today: sounded like thunder, or cannon fire, snaking down the train. This would happen on acceleration after deceleration or starting from dead stop. Would be most effective with some big honking woofers, cranked up: would scare the crap out of unwary visitors the first time.
And then there's the N de M boxcar I saw today in a UP freight (in the Bay Area, California). I've never seen one of these before; is this uncommon? Is this a post-NAFTA thing?