Caffeine overdose.

[Kiwidaninja]

Not much to say, aside from adding pure Caffeine as a chemical you can produce in Chemistry (With some effort), and allowing it to stop a heart in sufficient quantities, including putting some in coffee.

This means chugging a large amount of coffee will kill your character, say, twenty cups of it in ten-fifteen minutes would guarantee your heart stopping.

Im sure the character Bob Dolf will enjoy this. Heh.

[Dea Tacita]

Also a good way to kill someone as a chemist.

[Jamini]

I am reminded of a time, about fourteen months ago, where chemistry was totally overhauled and coffee could OD you with one cup. Oddly enough, a LOT of people kept trying to kill themselves with coffee.

Be careful what you wish for, folks.