A lot. And here's why. Partial list of Monk's phobia's and fear from this wiki:
Needles - I hate needles. A lot.
Death - I think we're all afraid of death.
Snakes - The only place I like them is under the mower deck.
Enclosed spaces/Caves - I need room to breath. Too much confinement and I get edgy.
Spiders - I'm no fan of them and can kill them without too much cringing. It's the big ones and the fast ones I don't like.
Public speaking - I'm much better at this than I once was, but it's still not a favorite thing of mine.
Chicken - Only if I eat it.
Frogs - Not afraid of them, just don't expect me to touch one.
Drowning - Even though I used to be a lifeguard, this is my most feared way of dying.
Food on my plate touching - This used to be a big issue when I was younger, but I've gotten much better. I even eat my food out of order now.
Sidewalk cracks - I actually avoid these when I can, but don't obsess about it.
And on a side note, if you watch me walk anywhere, you'll see me touch things as I walk around. Corners. Tags. Things that jut out. Kind of like Monk does with car antennae. And parking meters.