I propose the hydrogen cyanide - fluorine rocket.
It has the fabulous potential for a vacuum Isp of up to 380s, with a propellant mix density of 1023 kg/m^3, handily beating methalox mixes. It is non-cryogenic and burns at over 4000K.
Exhaust is 43.3% hydrogen fluoride.
As long as tested on a different planet, in a different solar system, I'm ok with this
What a NIMBY
Not in my low earth orbit.
Seriously, who needs foliage, or lungs, or skin, or bones....