FindBugs
FindBugs has got to be one of the coolest things ever. I saw this heralded as a great tool by the folks who do Java Puzzlers, only after downloading it and running on Genetic Image was I convinced of its supreme might and power. It found 2226 bugs in about 1149 classes in less than two minutes. Granted, most of those bugs are artifacts that the program uses code generation, but still!
Time to get working on some fixes…