Guides

Associate Sublime Text 3 with files that have no extension, which is not allowed through the usual configuration menu.

Download and run the following batch file as administrator:

associate.bat

assoc .="No Extension"
ftype "No Extension"=^"%ProgramFiles%\Sublime Text 3\sublime_text.exe^" "%%1"
assoc "No Extension"\DefaultIcon=%SystemRoot%\System32\imageres.dll,-102

Note: replace the path for sublime text with the desired program.
Note: also works for other extensions, but it should be easier to use the given configuration menu instead.