Hydrazine
Many satellites use hydrazine for their propulsion system (almost all of them, in fact). There are satellites that are still functioning 20 years after launch that have hydrazine propellant. It truely is a storable propellant. It's also corrosive and highly toxic. Hydrazine propellant tanks are typically made from stainless steel, as are the latch valves and many other propulsion system components. The tanks often have a rubber bladder inside with pressurized gas on one side to force the propellant out of the tank in weightless conditions.