This must have list was found on dotnet247:
QuickCode.NET
log4net
NAnt
NUnit
CodeSmith
Reflector
NUnit add-in
SourceBrowse
Filemon
FxCop
SecondCopy
I intend to compile a list of other must-haves
Related is the DXHogHunt which identifies which directories on your machine are taking all of the space.
Developer Rants 