I just saw a rattle snake with no rattle at the zoo, the description said it was unique to Santa Catalina Island. Here's some info:
ARKive - Santa Catalina Island rattlesnake videos, photos and facts - Crotalus catalinensis
I see rattle snakes weekly while biking and running on local trails. Usually Southen Pacific and Red Diamond, very rarely Speckled. Usually they are just sunning themselves laying across the trail, some coil up and rattle, one or two have struck and missed. Once I rolled right over the middle of a four footer, I just saw movement under my feet and when I turned around he was not very happy!