One time in my 20s,I went with friends to this huge bar. Guys would just randomly start to talk to me, being super nice, ask me if I want to dance, erx. I was thinking, man people are so friendly here, I love it. It took me at least an hour to realize I was in a gay bar full of horny singles. My friends made fun of me for years after that,for not realising where we were. To my defence, I was already drunk when we got there, but that said, I must have one of the least effective gaydar ever.