The TIP 120 is a NPN darlington transistor with a current gain of 1000 that is a good choice for interfacing many higher current or higher voltage loads to an Arduino or other microcontroller. It can be used to control DC motors, solenoids or strings of LEDs with minimal current draw from the microcontroller.
VCEO Collector-Emitter Voltage : TIP120
IC Collector Current: 5A
Hfe Current Gain: 1000