A few years ago, my friend and I were tieing one on here in Paris. We were looking for whatever might be open beyond 2am, and ended up at the Café du Départ across the street from Gare du Nord (biggest train station in Paris).
We ordered two 1664's, France's national beer. Not a spectacular beer, but not a bad beer by any means.
This beer was so foul. It smelled like absolute ass and tasted even worse. It must have been an issue with the keg AND the lines. Not one or the other, because it was just so disgusting.
We brought the beer back to the bar, told the guy we don't want draught, but rather a bottled beer. Wasn't much of a fuss, but still - the grossest beer I've ever had.