I don't think I could come up with an exhaustive list at the moment, but I do respect sharp objects, particularly when in someone else's hand and not my own. I also respect industrial and farming equiment, and anything with a blade in the kitchen. Fire, extreme heights, excessive speed, also respect those.
Really, anything that has the potential to harm you (and I mean that rhetorically) to the degree of losing a limb or your life should merit some degree of respect.
((And off to bed for me, will reply in the morning!))