"Get out of my way! Yes you! Stop taking up the whole sidewalk!" For the people who walk really, really slowly while taking up the whole sidewalk. You know they can hear you behind them, sometimes they even glance back, but they don't make any room.
Or how about:
"You're really pretty." I tend to stare at people, especially when they're pretty. I'm not being creepy, I'm an artist. Pretty people are the best drawing reference! But I feel like that will sound creepy or weird if I say it. So I say nothing, and let them think I'm being mean or rude.
