A new one that you don't hear of often, but was the mysterious culprit of a series of
date rapes and robberies, was
Scopolamine.
It's used in motion sickness patches, but it used in higher quantities, can cause delirium and retrograde amnesia.
In New York city, there were a string of out-of-town businessmen who wound up in the ER completely delirious, which would subside after a few hours, and all their money, credit cards, hotel keys would be stolen. Turns out they all went to the downstairs bars of their respective hotels, where they were all hit on by a woman. The guess by the police is that each time she slipped some of it into the man's drink, and as they went up to his room he'd collapse, while she'd loot everything. The side effect of the drug is that it leads to a retrograde amnesia, where you don't remember the events leading up to the event clearly. Also, there were no subsequent traces of the drug in the bloodstream.
Finally, a paramedic noticed a partially finished wine glass at one of the scenes and brought it in for testing. A gas chromatograph confirmed the drug Scopolamine, and a warning was issued to businessmen and tourists.
There was only 1 death, and I'm not sure of the reasons, perhaps the drug led to complications, although it could have been a mysterious overdose.