Another simple crayfish pattern is the Red Setter from New Zealand. There's a step by step in the FOTW archives (one of the earliest patterns).

The Red Setter is a particular variation of Fred Fletcher's "Fuzzy Wuzzy" series, which in it's original tie it was really just black squirrel tail for the tail, wool body, and black hackle palmered up the body. It eventually turned into the double hackle construction (one collar hackle mid body, and a 2nd at the head). Red Fuzzy Wuzzy uses red wool or cheneil for the body, Green Fuzzy Wuzzy uses green, and so forth. Red Setter's are sometimes tied with black tails, and sometimes fox squirrel tails.

These would be tied large for crawfish in lakes, say size 6 or 4, but I've tied small versions in size 10 or 12, and use them in rivers with some success as well.
- Jeff