Cow poop. Yes, I have definitely stepped in cow poop.
Adam Rifkin stashed this in Lolcats!
When I was little, I watched my cat make literally this same pose. Coming up to the porch, she stopped, looked at her paw, sighed (yes cat's can sigh!), looked away with what I am absolutely certain was disgust, then proceeded to spend a significant amount of time wiping her paw on the grass.
She was the most human-like animal I've ever known in so many ways even more than this.
I'd love to see a cat sigh. :)