Phobias are constant, irrational fears that afflict some people. Their fears should be taken seriously. They should never be made fun of or belittled. But, as writers, we can bless (or curse) our characters with phobias and make the story so much more interesting.
What happens if someone encounters the object of their fear? They could feel dread, nausea, or breathlessness. They could sweat excessively or lose the ability to think or speak clearly. They could lose control and become angry. Detachment from reality is a possibility, as is a full-blown anxiety attack.
Pick one of the following phobias and see if you can create a character with ballistophobia, chiroptophobia, or doraphobia. Have fun! Ballistophobia and Other Phobias