Heights and medical stuff for me.
Heights make me wobbly. It used to be a lot worse, but I've learned to control it to a certain extent. It's all in my head.
I can't take the sight of blood or other noticeable physical injury. Like the Theismann broken leg. I just brought myself to watch it for the first time a few months ago. (I was 3 when it happened, so I didn't see it live). The sight of needles makes me very uneasy; upsets my breathing and my heartbeat. I've cut myself pretty bad in the past (not in an emo way) and every time, I end up nearly blacking out. When it happens, I stop breathing, but realize it once I'm on the verge of going down and can usually catch myself and correct it.