Captain Cold's "Cold-Gun" is filled with elements such as liquid helium and liquid nitrogen, and is able to fire blasts of absolute zero -- minus 459.67 degrees Fahrenheit. These blasts are capable of the following power stunts:
Cryo-physics * Cat Burglery * Picking Up Women
The Legion of Doom * The Secret Society of Super-Villains * The Flash's Rogues Gallery
Deciding he would have to eliminate the Flash before he could successfully pursue a criminal career in Central City, Len Snart stole an unpublished scientific article that theorized a cyclotron might interfere with the Speedster's powers.
Breaking into a suburban radiation lab, Snart accidentally triggered its cyclotron, irradiating an experimental handgun of Snart's own design that had been set on a table nearby.
Confronted by a security guard while making his escape, Snart fired his irradiated pistol at the guard, freezing him into immobility.
After some experimentation, Snart donned a costume of his own design and began his new career as Captain Cold.