I watched Night of the Twisters once. I had to be in my Teenage years, but that movie just unnerved me so much. The part I remember that unsettled me the most is when the first twister passed over, and the kids are stumbling through the wreckage. One boy spots a man who he believes to be his dad from behind, and goes over to check on him. The man is sitting on a stump or something, dead. He had the same jacket as the boy's father, but it wasn't his father. Something about seeing that "body" and the possibility that it was the boy's father just horrified me.
I want to say it was seeing the bodies, death, destruction that scared me so much, but at the same time, I can watch Watership Down, First 48 and other true crime/forensic investigation shows no problem. I dunno what it was about that movie...maybe because I was younger when i saw it?