Speckled Hen - was in a Tilted Kilt and they had it on special. Waitress poured it from a bottle... Took a hefty swig and something was def wrong... One more tentative taste - and called waitress back over. When I lifted the bottle to emphasize my point, there was a definite "thud" of a sizeable something that should NOT have been there sliding from one side of the bottom of the bottle to the other... Three important footnotes: I did manage to not barf, I did not have the courage to check to see what IT was, and dinner was free. I would happily have paid for dinner to have avoided that experience!
Another example sits in my cellar at this very moment. A first attempt at a Cali Common went great right up to the point that I pitched the yeast into too-hot wort. 24 hours later, I knew that one was dead. My salvage attempt involved re-pitching the only yeast I had on hand: a dry wine yeast. I can only assume that I attenuated the crap out of the batch - there could not have been two molecules of sugar left in the batch. It's been dubbed my ESRB - extra "sucky" really bitter.
Cheers!