Nuns. Always a good roleplay, and less common than you would think given that the costume is easily obtainable.
The cowgirl is original though; I've never seen that one before. What part would I play? Go for Woody and the full Toy Story experience? How about finding a horse costume? Could play a steer that needs tying up, but I don't think I could take the branding. Very tempting to give Hayley another go.