Before he could walk, whenever I took him to a public restroom he would scream and crawl under the door of a regular size stall. The larger, handicapped stalls were big enough to avoid that though. He still prefers those.
Until about a year ago, he wouldn't go in the play structure tube/tunnels or tunnel slides. He is not afraid now that he is big enough to hit his head.
When he was small he had a fear of swimming pools with other people in them. He didn't like the movement of the water unless it was just the two of us in the pool. Now he takes 30 minutes at a pool before he convinces himself to get in the pool with the other people. He will go in with me without pause though.
I figured if claustrophobia was his biggest problem, well, then I could live with that. Ever since we went on that mine tour and he spent 45 minutes in the dark, in a cave, with sound resonating everywhere, well the fears have been mounting:
Astraphobia, Astrapophobia, Ceraunophobia, Keraunophobia, Brontophobia, Tonitrophobia- Fear of thunder and lightning;
Achluophobia, Lygophobia, Myctophobia, Nyctophobia, Scotophobia- Fear of darkness;
Acrophobia, Altophobia, Batophobia, - Fear of heights;
Ligyrophobia- Fear of loud noises.
I have crazy unbelievable stories about how completely he freaks out each time he encounters these things. How he won't go get his shoes out of his room after 3 pm because the curtains make it a little darker. Or sitting 3 feet off the floor on our bed post makes him scream like he's being attacked, but he will sit on the bed at the same height with no problem. Thunder he had no fear of before. We taught him "Boom, Boom" and he was fine with it; now any thunder has him freaked out.
At least 3 times a day he has to tell himself, "Nothin' scared of," to reassure himself. Oh, and I say it more often than that!
I think I have developed phobophobia- fear of phobias. I never know when a new one is going to crop up, and they all seem to have developed without any real provocation.
I got all these definitions at The Phobia List. That is a very exhaustive list, and it also makes for great reading.