It's completely situational.
Depends on how they stare at me. One gent was looking at me with a smug look at a table across from me so I batted my eyes at him. He smirked in a way that I found to be flirtatious and went back to eating. Another person stared with a soft smile on their face so I smiled softly back. I tend to "reward" kindness/compliments with the same back.
Idiots, however...different story.
Another guy called me "f**" one day so I blew him a kiss, waved, and said "So sweet, hun. Thank you! I love you too!" louder than he insulted me so people could see that I was talking to him. I'm not "gay" but whatever.
Another 50-something male idiot yelled something completely moronic at me from (get this) the back of his buddy's SUV. Like I am going to take a guy like that seriously? Maybe if the insult was more intelligent. He asked this:
"Nice outfit. Do they also sell it in the girl's section?"
I ignored him and din't even pay him a second glance, but what was going through my head was this: say whaaaaaa? No, sir, they sell dresses exclusively in the men's isle these days. Where have you been?
Another time a car full of men started yelling and saying that they were going to kick my @$$. They started to pile out of the car, so I puffed up and started to speak in the deepest "man voice" I could muster, yelling: "Party time, party time, party time!" Freaked them out so they went back into the car. Little did those bozos know I am ex-military and a one-time self-defense instructor so I wouldn't have gone down easy.
There has only been one time I was actually hurt by an insult, but it was because it was something my father used to use on me as a kid. That feeling lasted for a bout a minute until I got a lock on it: then I was mad at myself more than the ones who insulted me for letting my dad "win" again.
What I am hoping for is someone who can insult me with intelligence...but the thing is, the people who are intelligent enough to create any good insults are probably too intelligent to feel the need to say anything about it anyways.
I have had people take bets on my gender...no lie...but as an "androgynous tomboy" person that is exactly the kind of thing I should expect.