Shelf buttons have two methods of executing the commands associated with it: Click and Double Click. The problem is when double clicking to open the GUI the click command is also executed. For example double clicking to open the nurbs sphere options, will open the GUI and create a sphere.

This script will search out any shelf button that has a double click command and attached the command to a shift-click to all shelf buttons.

This will even affect user defined shelf buttons.

Following example uses the create nurbsSphere from the shelf:

Single Click: Creates a nurbsSphere
Shift-Click: Open the GUI
Double-click: Creates a nurbsSphere and Open the GUI

Please email me about bugs before leaving rating. So, they can be addressed. If you like it, let me know!