If we're listing most iconic threads from the Off-Topic section, no list would be complete without mentioning this one:
Let's talk about how hot Asian girls are. [NSFW]It is 187 pages of exactly what the title infers, with (NSFW) pics to back up the discussion.
This thread is the best topic on bitcointalk.
It ran for 3.5 years before it got locked. There was one member,
dragonbird, who posted there 414 times... as a matter of fact, every post he ever made on the forum was in that thread, lol. He was a dedicated expert on the subject.