Top 5 free .Net tools

On a daily basis I use some or all of the following tools for .Net development:

1. .Net Framework - it is perfectly possible to develop .Net applications without Visual Studio, this can be done by downloading the .Net Framework Software Development Kit and using your preferred Integrated Development Environment - Eclipse would be a good choice.
2. FxCop - an automated rules-based code auditing tool that audits your compiled code. Checks include: naming conventions, multilingual support, null reference checks for public methods and functions, to name a few. Rules can be turned off and on and new rules created.
3. .Net Reflector - uses reflection to reverse engineer .Net assemblies into managed code (c# or VB.Net). It can also decompile the .Net framework core libraries, which is invaluable way of both understanding the logic behind certain functions or improving your coding techniques (mind you there are times when you would like to rewrite some of the code :-)
4. NUnit - a port of the popular Java equivalent JUnit. A fast way to undertake Test Driven Development, especially with the next piece of software.
5. Test Driven .Net - an inspired piece of software that allows developers to run NUnit test cases from within Visual Studio. Literally right clicking a test case (and selecting Run test) to run a test or a test class to run a whole suite of tests! Cool!

Some other free tools I haven't used, but would love to get some feedback on are: NAnt (build manager), NDoc (C# automated documentation), CLR Profiler (performance profiles).

Also of interest may be the Mono Project that is a Linux/Solaris/Mac OS X/Windows/Unix implementation of the Common Language Runtime (CLR). This allows .Net applications to run on non-Microsoft platforms.