On Mac I often have files that are unknown to OS X. Opening the file results in a popup asking me to choose a file or search the Mac App Store.
I know that for files I can set the default program to open all files with that specific extension. What I am aiming at now is to set a default program on my Mac to open all files that cannot be automatically opened by another program. (Because 99% of the time I want to open those files in TextWrangler.)
So in short: I don't want to set a default program for files of a specific extension, but for all unknown files.