Yikes! That gives me the willies!
It's a timber rattlesnake. I haven't seen one in the wild before. It was kinda neat. The last time I saw a rattler, I was back home as a kid. I ran to get Dad to shoot it. He kept a pistol loaded with snake shot in the house at all times - not that we ever had that many rattlers in the yard. Maybe one every year or so.