If you cut wood, you need this.  They make impossible cuts possible, increase the safety of your saw operation by an enormous amount.  I make no cuts on my table saw without it.  Cuts never bind, never pinch, never saw burn.  Keeps your fingers OUT of the saw blade path.  With a little imagination you can set it up to literally do any cut on your table saw.   Setup literally takes less than a minute for complex cuts after you've used it a bit.  For simple push stick operation, setup is practically nonexistant.  It does the same job on the router table, eliminates snipe.  Best money I ever spent on a product in my shop, so I became a dealer.  I've been using them for over two years.  The only model I stock is the 200.  You need the extra attachments.   Click on the pic for a bigger picture of the GR200. 

To see them in action, go here.  But come back here to buy it ;-) .