Tripping over a rat, getting bitetn by the rat, and then needing rabies shots. Because this almost happened to me in Central Park it was dark, and out of the corner of my eye, I saw a dark blob-shape running perpendicular to my path, then felt its ratty little feet on my left shoe. I hurdled it just in time, and all the people behind me were having conniptions over it. I can still feel those little paws.