always gave me a heavy feeling in the pit of my stomach.
Comment on And no "water with a twist of lemon/slice of cucumber" goofs. Water isn't allowed.
[email protected]:Elemental mercury.
Based on the posed question and its limiting conditions, elemental mercury is a correct answer.
If you include materials which are liquid outside of "room temperature," things like magma and liquid nitrogen would also be correct answers.
Olive oil?
You wouldn't live long, but compared to the other options you're listing...