In my laptop. I rushed into the Apple Store, convinced that my computer was irrevocably dead (it wouldn't turn on, no trouble shooting with the help line worked), and when the tech came out, he asked if I had a dog with black fur. Apparently, a small amount of Hunter's hair had found its way into the vents of my computer, and blocked up some important stuff. It took about fifteen minutes to get it all sorted out, and we're as good as new, fortunately.
I don't know if it's the weirdest, but the worst place is the soft undercoat if one gets in your eye. It's nearly impossible to see it to get it out, yet you can feel it! That happens usually during the spring shedding.