I like threads that take some thought, threads that tell me interesting things about people, and threads I can make a useful contribution to, and unique threads.
There is a category of recurring threads I don't even click, on, but I am not sure how to describe it -- perhaps someone can help. The representative members are "what's your most ticklish spot", "which model would you like to tickle", "what reactions do you like", etc.
Another thing I like is if the title actually reflects what the thread is about. "A question", for example, is not a useful title.