People who smack straight into me when walking, especially when they run into me head-on. Yes, I know I'm shorter than most adults, but that doesn't make me invisible- watch where you walk!
Little kids throwing a huge fit right in public also really bugs me, at Disney or anywhere else. (Yes, I am aware that I was a kid once- the difference is the rare times my sister or I threw a fit, we were taken somewhere more private and properly disciplined rather than being allowed to annoy everyone else.) On a related note, and this admittedly happens more at other places than at Disney, I don't want to be dumped with the expectation of watching other people's kids while the parents ignore them. Just because I happen to be female and out in the same public place as you doesn't mean I'm your free babysitter!
Rant over.