Syria :p
Well - it is pretty much well known by now that "they" (various intelligences agencies) misjugded the amount of possible WMD (with intention or not - now that is the question).
Afterall it is has been all over the news, international as well as national (according to what I've seen) for a good while.
However - it is impossible to know if there isn't some stockpile in the desert somewhere, just hidden well. Iraq is still a pretty large country and with the war(s) and turmoil I doubt it would be difficult to actually hide WMDs.