What a silly thread!
But I'm feeling contrary so I'll bite.
I've used aikido in one door situation, six bar/street altercations (four times with success ie controlling the situation to get away or in one case to put someone down, once getting me kicked unconscious though I was very drunk, once getting me into and back out of a very bad position), several non-fighting situations like falling out of trees etc, many times in sparring against karateka, kungfuists and mmaists...
It worked in some cases. Anyone who tries to say scientifically if it works or not is deluded. It depends on the person and too many other (very) variables!