Are there any truly random sounds in the game, sounds that have a really low chance of being triggered, that you can think of off the top of your head?

No, but we could easily put something in. We have the functionality to do that. So like you said, trigger this sound, every time it triggers it's a footstep, but then randomly, like one in every thousand times, play a fart or something. That'd be easily doable. We've got some cool temp sounds. There's a horrific scream every now and then for a door.