Say you have an ATX power supply. Say you have some other piece of kit that likes ATX voltages, but isn’t ATX compatible. This solves your problem!

The ATX Breakout Adapter by Ron’s Computer Videos plugs into any ATX power supply and provides screw terminals for The standard +5v, +12v and -12v. Select the option with the Regulator (or add your own -5v regulator) and you can get that voltage too! A handy header is also provided to connect a switch or jumper for the Power On signal.