IntelliJ IDEA is an IDE tool for java. Available with commercial (license: US$499) and academic (US$100) licensing.
(Add $200 for extra support; not really necessary)

They also run a free EAP (Early Access Program) when they start working on a new version, where you can always use the latest and greatest version for free (until it's officially released). They also sometimes run special deals where you can get a personal license for only $200, and the license allows you to install a copy at home and at work (I think). --KenLiu

One of the best ever, IMO. Beautiful Swing interface, excellent refactoring support. If only they could minimize garbage collection pauses somehow. --KenLiu