A quote from:
http://www-pao.ksc.nasa.gov/kscpao/nasafact/count2.htm
Hypergolic propellants are fuels and oxidizers which ignite on contact with each other and need no ignition source. This easy start and restart capability makes them attractive for both manned and unmanned spacecraft maneuvering systems. Another plus is their storability — they do not have the extreme temperature requirements of cryogenics.
The fuel is monomethyl hydrazine (MMH) and the oxidizer is nitrogen tetroxide (N2O4).
Hydrazine is a clear, nitrogen/hydrogen compound with a "fishy" smell. It is similar to ammonia. Nitrogen tetroxide is a reddish fluid. It has a pungent, sweetish smell. Both fluids are highly toxic, and are handled under the most stringent safety conditions. Hypergolic propellants are used in the core liquid propellant stages of the Titan family of launch vehicles, and on the second stage of the Delta.
The Space Shuttle orbiter uses hypergols in its Orbital Maneuvering Subsystem (OMS) for orbital insertion, major orbital maneuvers and deorbit. The Reaction Control System (RCS) uses hypergols for attitude control.
Not too healthy to carry around but they are two liquids that don't like mixing.