Java Decompiler, Disassembler and Bytecode debugger. Decompiler supports Java 5 (e.g. generics, for-each loops etc). Debugger allows user to step through each bytecode and view program state. Contains Swing GUI.
JEST will be the Java bytecode engineering Swiss-Army Jackhammer.
It will include a disassembler, class browser, obfuscator, optimizer, class editor, and bytecode debugger, and have an intuitive GUI.