How can I bind a multitouch gesture to open a file with a particular application?
You can run an AppleScript file using BetterTouchTool, but I don't know how you get the selected file. Here's the script:

tell app "&lt;your application here&gt;" to open file &lt;file here&gt;


That will work as long as there's an application to open and a file to open. The problem is getting the selected file...