Scanning 27 controllers, 84 models, and 20 helpers, Towelie identified 14 duplicated methods. Towelie doesn't yet have the ability to identify methods which are very similar, so when I say it caught 14 duplicated methods, I do mean methods which were exact duplicates. (Although Towelie is whitespace-agnostic, so they may not have been character-for-character duplicates.)
That's what I did. Here's my IRB command history:
294: require 'lib/array'
295: require 'lib/towelie'
296: include Towelie
297: puts duplicated "../[client's app name]/app/controllers"
298: puts duplicated "../[client's app name]/app/models"
299: puts duplicated "../[client's app name]/app/helpers"
Towelie then printed out each duplicated method, right there in IRB.