James Avery created a list of tools that every developer should download.
This list contains .....
Snippet Compiler
Regulator
CodeSmith
Building a Custom Template
NUnit
Writing an NUnit Test
FxCop
Lutz Roeder's .NET Reflector
NDoc
NAnt
NAnt in Action
Switch Tools
here is the link of article that descries the every tools in great details...
http://msdn.microsoft.com/msdnmag/issues/04/07/MustHaveTools/