We all love Stackoverflow! A huge personal thanks for a great site to Jeff and everyone involved :) ... I hope this question can be a landmark in the question time-line and a chance for people to put a stake in the ground marking classic and good questions for future and current users.
Out of the 1-million questions, which is your favorite and why?
(not improvements, that's for MSO, if this isn't question 1m, delete me please!)