hypergolic

They're hypergolic with each other, meaning they ignite on contact.

Earlier versions of Grasshopper used hypergolic thrusters on the sides but they were scrapped in favor of the fins system.

The only hypergolic engines SpaceX uses are the Draco and SuperDraco, which were never on any first stage cores.

One of the uses of aniline is hypergolic rockets although its pretty toxic stuff and as not used for large rockets anymore.

"so rapidly hypergolic that no ignition delay has ever been measured"

In orbit, it probably uses hypergolic propellants, likely N2O4 and one of the hydrazines.

It is extremely likely it is the hypergolic fuel used for the on-orbit manoeuvring rockets.

It's room temp, stable, hypergolic, plenty of energy, it can even be a monopropellant.

It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water with which it reacts explosively.

It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured.

They're OK in small quantities, thus they show up in RCS systems, but making an entire orbital launcher using hypergolic propellants is a massive pain.

The engine installed in the aircraft currently uses hypergolic nitrogen tetroxide or hydrazine.

They needed it to be as reliable and simple as possible, so they picked hypergolic propellants which ignited spontaneously when mixed, so there was no need of an ignition circuit that might fail.

Failed launches, on the other hand, could contain unburned propellants, hypergolic fuels, radioactive or toxic payloads, and may come down as a blazing fireball on top of something that otherwise would have expected no more than a speck of metal oxides.