I have quite a few odd interests to be honest. I'd prefer not to share them as I have some sort of odd pesuado-internet-idenity-dignity left (which is insane as I have no real normal digity in real life). They aren't anything bad per say (well, some may say they're bad, but some will say everything they don't like is bad), it's just something I prefer not to be made public as they're private interests.
For odd interests I don't mind sharing without being asked first, I'll have to go with the interest in what exactly happens to things when you aren't looking at them. I actually think that, to some degree, perception is reality. And, going by that same way of thinking, it's entirely possible that things do not actually exist unless they are in your perceptive field (hearing, vision, taste, touch (which includes your insides as well), and smell). I think that's why I liked the episode 'Blink' from Doctor Who so much. It explores the concept to some degree.