[Death by Mirrors]

Two chemists walk into a bar. The first one says, "I'd like some H2O please." The second one says, "Sounds good. I'd like some H2O, too." Both raise their glass to each other, and after drinking the second one dies.

...but wait - there's more.

Two chemists walk into a bar. The first one says, "I'd like some H2O please."
The second one says, "I'll have a glass of water, too. Why did you say H2O? Like, I know it's the chemical formula for water and all, but it's the end of the day and there's really no need to intentionally over-complicate things like that in a situation outside of work."
The first chemist stares at his drink, angry that his assassination plan has failed.