Eh, I mentioned several, but none of the others were as interesting so I didn't post them above. Here they are for completeness. Both were from the 80s, when gender and orientation were more taboo.
One was a male elf whom another party member, a female human wizard, had a crush. The elf was friendly but just seemed not to notice - he was urbane and polite with everyone. Almost Spock-like in interpersonal relations, though he could really get up a hatred for orcs. Things proceed with this unrequited crush for a while (and many levels) and then the whole party was at a, well, party where the main drink being served is a powerful aphrodisiac. The DM had us making rolls against poison with increased effect for each failure. (This was AD&D 2nd - I think the save was "Petrification/Poison/Death Magic".) After I failed two and while the wizardess had been next to throwing herself at my elf, I wasn't RPing the return. The DM, knowing I'm a good RPer, pointed out that I should be randy at the least. I agreed. As the night went on, it eventually became obvious that the elf was, in his urbane and polite way, trying to put the moves on the swashbuckling and charismatic leader of the party, who was also male.
Nowadays that wouldn't be a thing, but for teenagers in the 80s it was unexpected. Good RP came out of it, and a very, very disappointed wizardess.
The other story was around gender, and also in the 80s. Had a really cool painted, moderately armored mini with a chainmail mask under a hood. Who would wear something as uncomfortable as a chainmail MASK? Well, someone trying to hide not just what they look like, but the very curves of their face. So, the idea of Lady Jenna was born, fleeing an arranged marriage and taking on a male persona of "Jorum Farstalker" who had an aversion to being touched.
Was found out by the cleric (back then heals were ranged touch), but she kept my secret. Was all good until one of the other players introduced a paladin to replace his previous character. "Jorum" dropped in combat, and the paladin used his lay-on-hands and found out. He broke it to the whole party, wouldn't lie.
The only problem is that Lady Jenna was pursued by her powerful family whom she was causing no small deal of embarrassment on running out on the wedding. While I am sure the DM could have made it a cool part of the campaign, her personality was more that this was the one flaw she couldn't fight, only hide, so she left the party and took up a new persona. And I rolled a new character.
I did get a chance to play her again elsewhere in the same world (DM ran a lot of connected games). She's a somewhat tragic character to me, for all her heroics he never faced her family and let the secret define her.