The flying monkeys in Wizard of Oz scared me when I was very little. Jaws probably qualifies as horror so may not count here, but I saw that when I was too little to see such things, and the shark biting Quint traumatized me considerably.
I must be weird. I loved the flying monkeys in Oz. I saw Wonka at the Cinerama Dome when I was five, and it wasn’t till recently when someone suggested it was scary that it had ever occurred to me anyone would.
OH! Wait, I got a good one: Little Shop of Horrors. The man-eating plant freaked me out, especially given the ending.
I wasn’t so scared of the flying monkeys, but in Return to Oz, the woman who had all the different heads terrified me. When Dorothy is sneaking through the sleeping heads and they wake up and start yelling and then the headless body starts coming after her… Yikes. That one scared me a lot.
The 1986 animated film When the Wind Blows, based on the Raymond Briggs graphic novel, is freaky even today.
It’s basically an animated version of the Day After and Threads, being an anti-nuclear war film. The deranged animation, the use of animation with three-dimensional sets (meant as a middle finger at the UK Protect and Survive films) and the fact that the character die at the end painfully from radiation poisoning makes this nightmare fuel!