Here's a list of universal human behaviors that have been assigned to gay men and straight women. When I do these things, they are so offensive that people assume or insist that I'm gay or transgendered, because that's actually less offensive than a straight man claiming aspects of behavior that have been made inaccessible.
Good posture, paying attention to my grooming - this would only be acceptable if I were black.
Bright colours, and especially baby blue, sea foam green, yellow, and pink. Again, ok if I were black.
Any hip movement while walking. I'm supposed to walk with my shoulders, somehow.
Wearing clothing that has been recently assigned exclusively to women (skirts, stockings, tunics, hats that are not sports-derived, tights, high-waisted pants, anything tight or form-fitted, pants that stop between the knees but above the ankles).
Appreciation of other men's beauty or acknowledgement of male beauty in general. Straight girls, of course, are expected to be able to speak to each-other's attractiveness, and give each-other compliments.
Respect for women, and conspicuous lack of misogyny, non-participation in socially-acceptable sexism.
Refusal to be sexually aggressive.
Lack of interest in sports or other activities that are not co-ed. So, because I don't want to watch two teams of men in competition, I must be gay. I feel uncomfortable when surrounded by people of all the same gender, and that's not ok coming from a straight man.
Discomfort with "just get the job done" thinking, and a preference for a balance of thought and action, planning and production.
Reaching out for help from friends or professionals. I'm told to stop beating myself up (always as a non sequitur), "man up" or some other variation of "keep it to yourself, solve it yourself," and most important is the implication that I'm thinking too much - overthinking. The implication is scary: men are supposed to do society's intellectual thinking, and women are supposed to do our introspection for us.
Speaking in a light or airy way, instead of a heavy, hoarse way.
Aversion to shouting.