Some tools I use:
CodeRush - If you haven't tried this then you should $249 (when I last checked) for mere mortals, this wonderful tool is also available for FREE if you're an MVP and although not widely known, it includes RefactorPro in the price.
RefactorPro - By far the easiest way to refactor your code. Simple interface, quick to operate. A joy to use. $99 if you don't want CodeRush (you mad fool you :P)
Reflector - For anyone who's curious how stuff works under the hood
Expresso - To say this is a WYSIWYG Regular expression tool does it a great disservice.
SketchPath - As above but for XPath expressions
MyGeneration - Free Code Generation Tool.
Windows Live Writer - I'm writing this post using this wonderful tool. So easy.
OmeaPro - My nntp/ rss reader of choice.
AutoHotKey - Windows automation on steroids.
NiftyWindows - AutoHotKey derivative program with many gestures and hotkeys prearranged.
Unlocker - Don't you just hate it when the file you need to delete/move/alter is locked