Wagtail
Horse servant
I've thought of another one, although it doesn't seem to happen as much as it used to. If a poster is getting some flack for saying/doing something daft, someone drags up ancient, totally unrelated threads where the OP had also been unreasonable/in the wrong/acted a bit mad and use it to rip into them. It seems too personal, unfair and attacking the poster not the post to me and it annoys me.
Ooh, I'd forgotten about THAT one. I have seen it happen quite recently. I think that behaviour is completely under the belt, and says a lot about the person using that tactic, and it's not good.