Feminists and allies may want to arm themselves with good sexism comebacks in advance, particularly in person.
Note that this page is not a guarantee! These comebacks may not work. Or in a particular situation they might turn into Bad sexism comebacks. This stuff is hard, no promises can be made.
Characteristics of good comebacks.
They are simple. Very complex jokes or shaming tactics are hard to remember and they run a high chance of playing into homophobia or other gender problems, see bad sexism comebacks.
They are short. You usually cannot convert someone to feminism in a single call-out. There is seldom much point in a long argument after a sexist comment. Often, all you can do is disapprove.
"I don't think that sounds as funny as you want it to sound."
Preemptively destroys "but everyone thinks this is funny".
"Why do you think it's okay to say something like that?"
Preemptively quashes "I was only joking". Better than "Who let you think it would be okay to say something like that?" which leaves room for a "You're a prude" response.
End the line of discussion. May cause conversation participants to question where they crossed a line.
"Wow, women X's are so rare/unusual": reply, "That's why it's so important that I exist"
Shift the dialogue from an othering to recognition.
alternative: "Wow, women X's are so rare/unusual": reply, "Would you rather have a male for this? Do you also have any racial or religious preferences?"
deflection, though this may be contentious in its use.
"Excuse me?" / "I'm sorry, I don't quite understand what you're trying to say. Could you state it more plainly?" / "What do you mean by that?''
Chime in. Cause the speaker to reflect. Be prepared to follow up. Especially useful with people who are open to conversation but harbour misunderstandings of feminism.
"It sounds like you are implying <sexist thing>. I'm sure you don't really think that. <change subject>"
Exerts some social pressure against stating <sexist thing>.
"That was sexist."
Just saying it out loud is a good comeback.
"That was sexist, and that is not acceptable here."
If you are in a position of power, such as a boss or community leader, you can create, point to or enforce boundaries in response to an incident.
"Hey dude, not cool."
Simple vernacular disapproval of the action, rather than the person.