While I'm a lesbian, I make a point to absolutely humiliate any man who has the audacity to come up to me and flirt while I'm minding my own fucking business trying to enjoy my day (see edit below for clarification on what I mean by "flirt" here). I'm fully aware I could just say "I'm a lesbian, fuck off", and most of those guys would fuck off (please note, this also reveals homophobes that claim I just haven't been with a "real man" yet, and those guys are absolute assholes that won't take a fucking hint), but it's so much more fun to absolutely destroy their ego instead.
*Looks over them like I'm checking them out*
*Laughter as if they're pathetic*
"No, hun. I have standards"
*Shoos them away*
Granted, I open myself up to a lot more danger by doing this, because it often pisses them off, but it's so worth it to see the dejected look on some of their faces. Bonus points for destroying whatever they say in response with more ego-shattering insults.
NOTE: I recommend other women don't follow in my footsteps without some solid self-defense training and a can of maximum strength pepper spray. I cannot stress enough that there are men who do not take blows to their ego lightly, and will get very aggressive.
EDIT: I didn't think this needed to be specified, but since y'all are making such a fuss in the comments, let me elaborate. It's sexualization and objectification that get me heated. If you come up to me and compliment something genuine about me that isn't some inherited part of my physical appearance (i.e. telling me you like how I did my hair today, or how my outfit comes together, or complimenting something you saw me do), I'm not gonna have any problem with you. Or perhaps you just treat me like any other human being and start a conversation and get to know something about me first. But if you come up to me and say shitty pick-up lines or say (or imply) that my body is making you horny, I'm gonna have an issue. Especially if I'm just trying to mind my own business because I don't like being approached by men when I go out. It just so happens that almost every time I'm approached by a man who intends to flirt with me, they fall into the latter category. You wanna be respectful? I'll politely turn you down.