Ya'll have some great stories. My own are all encounters with small animals:
Working on an AC condenser I had an extension cord run along the side of the house. Out of the corner of my eye I see my cord sliding away. I look over and that's when I realise it's a copperhead snake.
While working in a low basement I felt something in my hair and, thinking it was just some cobwebs, casually brushed it out. And watched as a black widow fell down the front of my shirt.
Had a very unpleasant experience working on some j-boxes that had been covered up by a dropped drywall ceiling. I could get into the 24" space between the dropped ceiling and the original ceiling through the plumbing access in the bathroom. Only after I squeezed down there did I see all the home-owners's house cats which were using the space to hide from me, and apparently also as litter-box: There were mounds of cat-poop maybe a foot in diameter and several inches high.
A funny one I was present for was fishing wire into an attic for a light switch. My buddy is in the attic getting ready to drill the top-plate, and I'm on the floor below him. Suddenly I hear him scream "SQUIRREL!" and then his leg is sticking through a hole in the plaster ceiling. Apparently it spooked him a little when it popped out of the insulation.
-John
