I had one cat that was terrified of balloons and balls. He was also terrified of thunder storms and would always pee wherever he happened to be cowering.
Of my three cats now, the Bengal is afraid of seagulls. We found this out during a trip to grab a snack at Burger King years ago. She loved going on car rides with us until she saw seagulls in the BK parking lot and flipped out and tried to hide. After that, she never wanted to go in the car again.
The DSH is scared of cooking pans and lids. If he sees one in my hand or sees me opening the cupboard where I keep the lids (the pots & pans are kept in an overhead rack above the island) he runs. Very weird!
The Tonkinese isn't afraid of anything but the water squirt bottle since he knows he'll be punished for attacking the Bengal. He often tries to "make friends" with the bottle by rubbing his face on it. Nope, the bottle is still NOT his friend!
I have never owned a cat myself, but there are plenty of cats owned by my relatives and friends.
Most cats I have seen are afraid of strangers. They are extremely cautious around anyone who isn't their owner. They might look at you from a distance before retreating if you continue to walk into that direction.
Many cats also seem to be avoiding dogs with the exception of puny dogs. I wonder how pet owners with both dogs and cats are able to get them to like each other.