Drawing a glowing line from one point to another on update

What I'm looking to do is start drawing a line on mouse down and and stop drawing on mouse up. A straight line from the mouse down position to the current mouse position on update.

Oh, and it has to glow too!

I've looked and trail renderer, line renderer and dabbled a little with particles, but I'm not sure that the best method would be.

If you have Pro, the GL stuff draws lines, and there is Vectrocity in the Asset Store http://ippomed.com/wordpress/a-new-addon-for-unity3d-vectrosity

If you are talking Editor script, look at Gizmos.