I recently thought up an idea for a way to make an in-shot gun-flare.

1: Get a little bit of aluminium foil.
2: Use some stick to put it at the tip of a gun.
3: Shine a torch or two at it and try to reflect as much light as possible into the camera.
4: Take a picture.

I probably could have done better.  My aluminium got a bit wrinkled, and it's a tad bit big, but it would be an interesting thing to do if you wanted to specifically avoid using computer effects, or perhaps you just don't want to go to all of the trouble involved in adding one in there.

This probably is a bit too small of an idea to merit its own topic, but I couldn't think of a better preexisting topic where I could post this, and I just really want to share the idea for anyone looking for more brickfilming ideas.