I’m sure you all know of the standard decompilers such as ILSpy or Reflector. They both rely on Mono.Cecil to read assemblies, which is quite a fragile library when it comes to loading obfuscated files. Because of this you should use DnSpy, a ILSpy mod by 0xd4d which uses dnlib to read files instead of Cecil. It’ll load obfuscated files and allow you to browse them (IL->C#/VB conversion still might crash).
Check the source out: DnSpy
or download compiled binaries: http://www.multiupload.nl/EF76M8JP8I