LEDs - those blinky things. A must have for power indication, pin status, optoelectronic sensors, and fun blinky displays.
Features
Efficiency: LEDs emit more light per watt than incandescent light bulbs. The efficiency of LED lighting fixtures is not affected by shape and size, unlike fluorescent light bulbs or tubes.
Color: LEDs can emit light of an intended color without using any color filters
Size: LEDs can be very small (smaller than 2 mm) and are easily attached to printed circuit boards.
On/Off time: LEDs light up very quickly
Cycling: LEDs are ideal for uses subject to frequent on-off cycling.
Dimming: LEDs can very easily be dimmed either by pulse-width modulation or lowering the forward current.
Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics
Lifetime: LEDs can have a relatively long useful life.
Shock resistance: LEDs, being solid-state components, are difficult to damage with external shock.
Focus The solid package of the LED can be designed to focus its light