Enderman

The Enderman is a mob introduced in version 1.8; The Adventure Update. . The Endermen are depicted as 3 meter tall, black creatures with long arms and legs. They also seem to have the ability to pick up and move blocks around. They are generally peaceful. If you look at them, by placing your crosshair directly over them, they freeze, stare back at you, and become hostile. They stay frozen as long as you keep looking at them. When you look away, they will run fast towards you teleporting up to once every second to get to you faster.

Trivia

 * The name "Enderman" is derived from the internet phenomenon Slender Man, due to the mob's similar looks. Its name was given by Notch in a Reddit thread.