I'm sure I mentioned the time I logged an old bottle of n-butyl lithium in the fume hood that needed disposal in a place that didn't contain water because splody will ensue. Then I forgot about it until five blokes in full armour from the actual bomb squad turned up to remove it with metre-long tongs. I'd been holding it in my hand and giving it a shake not so many days before.
(To be fair, it's not that bad, considering some of the other stuff knocking around, we had an entire cupboard of potent mutagens that women weren't allowed near on the vague off-chance they might be unknowingly pregnant. I had a small tub of ricin on my desk, I think 5g. Happy times.)