There are a number of questions or answers on Stack Overflow which, for one reason or another, stand out from the rest in a measurable, objective way.
Please edit the community wiki answer below, adding particularly extraordinary questions.
While most of the initial outliers will be the easy to find "highest voted" and so forth, I'm particularly interested in having people add those that are not as easy to find. Longest answers. Longest code blocks. Highest voted comments. Longest period of time between question being posted and receiving an answer that was accepted. there are doubtless others that are notable for various reasons.
Please only call out posts and comments - this is not the place to list users that are outliers in one way or another.