We once rode Space Mountain with the lights on....you'd be surprised at how UNscary it really is!!
I have never ridden SM, because I was always intimidated by it, but last visit we were on TTA which stopped right at the SM viewing window and the lights were on. I was amazed to see that there really is nothing to it, the only intimidating part is that it is in the dark!! It looked like a very tame ride, can't wait to try it next time.