Hi y'all, I just joined this group.  Man, can I relate to what some
of y'all are saying.  My unusual phobia:

I'm afraid of fish.  Ichthyophobia, perhaps?
I don't get it, either.  When I was little, I loved to go to the
aquarium (I live not far from the New York Aquarium, which is huge
and wonderful), but I was afraid of swordfish.  Since aquariums tend
not to have those (or at least, I don't remember ever seeing one), I
was fine with them.  I'd sit on the little shelves that jutted out to
keep people from leaning on the tank glass and watch the fish in one
tank for long stretches.  I'm sure I bored my parents to death.  I
was deathly afraid of the undersides of rays and of sharks, but those
don't seem all that abnormal.
Then one day, I encountered a creature that would change my life
forever, a fish so absolutely horrifying that its name shall forever
haunt my nightmares: the unicorn fish.  Yes, you heard me right.  I'm
afraid - and I mean AFRAID, I can't even look at a thumbnail image of
one without having a strong urge to shriek and RUN AWAY as fast as I
can, possibly while peeing in terror - of something called a "unicorn
fish."  Like it's not humiliating enough to be afraid of fish, but
the one that inspires true terror has the most benign name you can
imagine.  I don't know what it is about them, something about their
faces. 
Over the years I've managed to desensitize myself to all other fish -
most triggerfish (which I find oddly creepy), sharks, rays, even the
deep sea anglerfish (I'd still rather not look at those, but I CAN
look at a picture of one without running and hiding), but the fucking
unicorn fish remains as scary as ever.
So I'm basically afraid of all fish, but I'm also fascinated with
them.  My true phobia lies in the unicorn fish.

I've got various other phobias, but most of them are
more "acceptable" and not fears that people mock.  Although I have a
few family members who tease me about my fear of clowns, I find that
most people don't like those scary beings.