About 30 years ago, I'm clearing a building site. It's at the edge of an old overgrown cornfield, so there are huge trees along the edge of the old woods, and 30 - 40 foot trees in what was a field. We began felling the smaller trees, but they were full of grape vines, and were busting up the branches of bigger maples and beech we had to save.
I go get this huge old wooden 40' ladder to cut vines from. The kind you hate to climb down and move. After a while, I'm getting dumb, reaching out way too far and one-handing vines with the chain saw. So, I'm leaning out really far, one hand and one foot on the ladder, and this giant Black snake drops off the vines above as I finish a cut, across a branch and right in face. It must have been sunning itself on the mat of vines or something.
It was the most startling thing I've ever experienced. I've been more scared, but never more instantly shocked. I still can't believe I didn't at least drop the chainsaw. That snake was over 6 foot long, and as big around as my wrist. I haven't seen a bigger one wild up here.