Obfuscar is a basic obfuscator for .NET assemblies. It uses massive overloading to rename metadata in .NET assemblies (including the names of methods, properties, events, fields, types and namespaces) to a minimal set, distinguishable in most cases only by signature.
For example, if a class contains only methods that accept different parameters, they can all be renamed ‘A’. If another method is added to the class that accepts the same parameters as an existing method, it could be named ‘a’.
It makes decompiled code very difficult to follow. The wiki has more details about WhatItDoes.
Babel is an obfuscator for .NET assemblies. Babel is a console based application, if you like you can run Babel from Reflector using the addin made by Jason Haley: