I was hiking up around my family's cabin about... ten years ago. We had left our bikes a ways back, and were walking along this trail near some farms.
All of a sudden, a huge grey dog (I think a doberman or a greyhound, but I dunno) burst out of the bushes in front of us. We stood still for a second, to see if it was hostile, and then it barked and moved towards us.
We were young and stupid, so we panicked and ran the other way. For some reason, we managed to outrun the dog - maybe it never really started to chase us.
However, the path had a ton of logs running horizontally across it. One of these logs ran diagonally though, and had a branch the size of a finger sticking straight up from it.
As I jumped over this particular log, that branch caught my knee, and tore into it. I fell forwards as it ripped a good chunk out of my knee, and I tumbled through all the wet leaves and mud. I got up and tried to walk again, but couldn't.
When I looked down, there was white, stringy flesh hanging out of the wound, and it was bleeding all over my leg. I limped (with help) back to the bikes, and then we managed to make it home, though it took a while.
My dad really enjoyed pouring the peroxide all over my knee. Didn't hurt that bad, actually, which was really surprising.