Flog reports the most tortured code in an easy to read pain report. The higher the score, the more pain the code is in (and harder it is to test).
% ./bin/flog -g lib
Total Flog = 1097.2 (17.4 flog / method)
323.8: Flog total
85.3: Flog#output_details
61.9: Flog#process_iter
53.7: Flog#parse_options
...
gem install flog
git clone git://github.com/seattlerb/flog