deobfuscates the following:
clisecure, cryptoobfuscator, dotfuscator, eazfuscator, smartassembly, xenocode, .net reactor

this is generally used by people who are interested in taking a peek at the source code or cracking/patching it.

here is the guide:

first you need to download a tool called de4dot https://github.com/0xd4d/de4dot/downloads
edit: new download link: https://bitbucket.org/0xd4d/de4dot/downloads
extract it to c:/ and rename it to de4dot for easy access.

put in the program you want to deobfuscate in the directory of de4dot

now open up your command prompt (start > cmd) or windows key + r
now type in cd de4dot; you should now be in the de4dot directory.
type in de4dot <name of program you want to deobfuscate>.exe (remove the <> brackets ex. hf.exe).

alternatively:
drag and drop the program (exe) you want to deobfuscate onto de4dot.exe

wait a little bit.

now you should get a new file called <name of the program>-cleaned.exe.

you are now able to open this up in net relector or simpleassemblyexplorer