This nifty Puff Handle by Z-saw keeps your cutting line visible by applying a puff of air to the cutting site with every stroke. From Core77:

As a part of our Hand-Eye Supply duties we test out new product. Yesterday we gave this intriguing Japanese Saw a tryout! It incorporates an internal piston system that “puffs” air from a blow hole on to the work piece using the kinetic energy from the worker’s hand motion. The “puff” clears away saw dust so that you can clearly see your cut line. It may seem gimmicky but as Japanese saws enable extremely precise cuts this is an indispensable feature!