Orbs!
I love orbs. They glow, they fly, they are completely mysterious - what's not to like?
Admittedly there is ONE thing not to like about orbs, and that is their tendency to be mimicked by floating bits of dust or flying insects. One reason I really like "Ghost Hunters" out of all the paranormal investigations out there is that Jason and Grant almost always rule out "evidence" of orbs for this reason.