Lutz Roeder's .NET Reflector is an excellent tool ...

Lutz Roeder's .NET Reflector is an excellent tool for analyzing and understanding .NET assemblies. The decompilation feature is top-notch, allowing me to easily inspect the underlying code and dependencies. The user interface is intuitive, and the overall performance is great. I've been using it for a while now, and it has become an essential part of my development toolkit.