Reflector is a class browser for .NET components and assemblies. It features hierarchical assembly and namespace views, type and member dictionary index search, type reference search, custom attributes view, IL disassembler, C#/VB decompiler and viewers for C# XML docs and MSDN help. Assembly dependency trees, supertype/subtype hierarchies and resources can be inspected as well. Function prototypes are displayed in C# and VB syntax.
This is an amazing tool, but the decompiler part just kicks ass…