My worst was on the way to work last January in the 80 240D. I was passing through a small town and heard a light clanging noise. All guages looked good, so I carried on figuring that something minor had come loose that would require tightening. Wrong. About 5 minutes later the alternator lights came on, and the temp guage shot up to the top peg instantly. I shut it down, and was immediately greeted by massive quantites of steam. Car was fatally wounded by the stupid harmonic balancer of all things shearing it's retaining pins. Once I do finally find a crankshaft for it, I'll rebuild it as I couldn't bring myself to strip it down to sell off the parts.
That week was just plain horrible. I was in the hospital two days later over an infection on my foot.