TEC (Thermoelectric Cooler) units with preattached leads. When voltage isapplied, one side of the TEC will get cold while the other side will get hot (you can switch the voltage to flip the direction of the temperature difference), or you can use them in reverse to generate electricity.

These amazing semiconductor coolers get ice cold in minutes or heat to boiling by simply reversing the polarity. What you can use is for temperature regulation of diode lasers, but they can be used for numerous applications from CPU coolers to alternate power sources, or even for your own custom car drink warmer/cooler (power from cigarette lighter).