Honestly Homestuck was a big one for me. Specifically it was seeing Aradia go from emptily moving through life as a ghost to her fun, energetic character once she is revived and being like "Wow, that's so cool! I wish i could do that". Hell, Psycholonials was what pushed me into thinking of myself as not a man, even if I still hadn't figured it all out yet.

This one's pretty obvious, but I Saw the TV Glow is kind of what pushed me over the line into admitting to myself that I was definitely a woman. It was just kind of like "I relate to this too much for there to be any other explanation".

Thinking back to my childhood, though I was a long way away from any kind of gender revelation, I remember playing Portal 2 and getting a weird sense of joy whenever I saw myself through a portal. I hadn't played many games at that point, and the ones I did were often stylized or featured a male protagonist, so something about being able to see that the what I was thinking of as "myself" in that moment was a girl definitely impacted me in a way that I didn't really understand at the time.