Watch your fingers, these guys pack a powerful punch. Caused not by the two halves of the claws making contact but "originates from the collapse of a cavitation bubble".
http://stilton.tnw.utwente.nl/shrimp/ : Good link with links to video of pistol shrimp snapping, see below (web site has more video, audio and photos).
http://news.nationalgeographic.com/news/2001/10/1003_SnappingShrimp.html : National Geographic article
Slow-mo video of a "snap":
Front view slowmo:
http://stilton.tnw.utwente.nl/shrimp/ : Good link with links to video of pistol shrimp snapping, see below (web site has more video, audio and photos).
http://news.nationalgeographic.com/news/2001/10/1003_SnappingShrimp.html : National Geographic article
Slow-mo video of a "snap":
Front view slowmo: