Jurassic Park for me. I had an amazing JP jumper when I was like...maybe 6. It was far too big for me but I loved dinosaurs. Naturally this meant I wanted to watch the film because...well I'm 6 and it's got dinosaurs.
Ultimately I ended up watching it with my Mum and Dad. We got as far as the iconic T-Rex chase scene and I told them to turn it off. Didn't go near the film for another few years.
I've now got my own 6 year old. There's no scenario I could envisage where I even consider letting her watch a film as gory, tense and frightening as JP.
The Blob, the 80's version. I was around 5, snuck into a room where people were watching it. The guy being dragged into the sink made me terrified of using the toilet and I developed a turbo-pissing technique to minimise time spent on the bog.