The Saunders Pro Deadly Quiet!!
I bought one last year and am definately impressed! I made the mistake of keeping it on all year for leagues and 3d and wore the rubber stop out pretty quick. No problem , I called Saunders and they had a new and improved rubber stop , so they sent me two extra ones for no charge. I put mine on the week before the season starts just to get a few shots through it. Even if you already have all of the other shock doohickys , you'll notice a difference.
Here's their websitehttp://www.sausa.com/pp4.html

"Nocked,cocked & ready to rock"