Java Static Code Analysis
petermartinblog.com
petermartinblog.com
This has revealed many bad habits and allowed us to correct them through review comments prior to changes being submitted. It's also shown me just how "legacy"[2] our code-base is, but thanks to sonarqube (which runs PMD and FindBugs as part of its analysis) we're improving.
[1] http://www.sonarqube.org [2] http://www.amazon.com/gp/aw/d/0131177052