HHN 18 was the first time I ever actually got scared.
We were going through The Hallow when it was still light out, so our eyes hadn't adjusted to the darkness yet (silly us, it was the second house we went through on the first night). We were going through one corridor that was barely lit, just enough to be able to see some dark shapes floating in front of me. I pushed one out of the way, and it was hairy and wet. Confused, I continued onward.
Suddenly, there was a crash of thunder and lightning that showed a disgusting, very realistic severed head not 8 inches from my face.
I promptly screamed "Holy Jesus shit!" and ducked, running like a linebacker under the rest of the heads to the end of the corridor.