I apologize if this is already well known, but I discovered it by accident and thought I'd share...

If you have a lens with a built-in neutral density filter, you can (during a correctly exposed shot) quickly and sporadically turn the filter on and off. The result is a great 8 or even 16mm flash that, if timed right in editing, really looks nice. Here's an example:

Be sure 'view width' (below image area) is set to widescreen before it plays.

http://media.putfile.com/example68