Sun’s Java VisualVM
VisualVM is an interesting tool, and the fact you don’t have to instrument your applications to use it is rather nice. Real-time monitoring of you application is very nice and the ability to take snapshots or heap dumps is also very useful, but their heap analysis tool needs some work.
Compared to some other heap analysis tools I’ve used VisualVM needs a lot of work. Having said that being able to take heap dumps as you manipulate a system in real-time is very useful, and then using another analysis tool seems like the best option (note I haven’t tried using another analyzer with visualVM’s heap dump.)