Text editor for Mac that will open any file

For Textwrangler - You just need to drag it to the Documents draw and a blah.hdl file opened perfectly well for me. It even will try to open binary files that way, but may ask you for an encoding to use...

To change it asking what to do you can track down a setting in the Textwrangler Text Files preferences:

Also, works for me perfectly well (renamed a file blah.hdl and dragged) in Textmate. In fact I can drag anything into Textmate and it will "open" it (no snarky-ness intended ;-)

Drag-and-drop works for MacVim. It also works in Aquamacs.

Edit: Dragging-and-dropping a PDF into TextWrangler did not work. Apparently TextWrangler tries to figure out whether or not you should be opening that file in a text editor.