Northern Pacific Rattlesnake (Crotalus oreganus oreganus).
As I was taking pictures of the bees and crab spiders I got a bit of a "gitchy feelin'" and turned around. Lo and behold, this beautiful rattler was five feet behind me at the creekside! It was very relaxed, just stretched out and waiting for me to leave. As I got closer to take pictures, it did nothing but flick its tongue in and out every time I moved. Totally chill, and a shared moment. I left for a few minutes and when I returned it was drinking water from the creek. One of my favorite snake encounters.
Should have gotten some extra ambient sound to replace my lens and breathing noises, but oh well.
Mt. Diablo State Park, California.
Micro-Nikkor 55mm f/3.5