Android 19 is an android created by Dr. Gero. He only seemed to exist in the present timeline.
Android 19 has chalk-white skin and is extremely fat, with a high-pitched voice. Like Dr. Gero, he can absorb energy through small orb devices on his hands. He is also bears a striking resemblance to that of Majin Buu.
Dr. Gero was made into Android 20 by 19. Together, the two androids attacked a city where they encountered most of the Z Fighters. 19 fought Goku, who, with his Super Saiyan powers, had the advantage, but when Goku shot a Kamehameha at 19, 19 absorbed it, increasing his power. He then beat up Goku, who then was attacked by a heart virus. 19 beat Goku up while he was unable to fight back, and began draining his energy when suddenly, Vegeta attacked him. As Yamcha got Goku back to his house to take the medicine for the virus, Vegeta transformed into a Super Saiyan, revealing for the first time that he had achieved this transformation.
Vegeta fought 19 and beat him up. 19 grabbed Vegeta's arms and began draining energy from him, but Vegeta, despite losing a bit of energy, pulled 19's hands off. From 19's reaction, Vegeta confirmed a question he had asked earlier, that androids do experience fear. 19 tried to run, but Vegeta destroyed him with a Big Bang attack, leaving only his lifeless head. Trunks saw the head when he returned from the future to fight the androids, and did not recognize him at all.
Dragon Ball GT
In Dragon Ball GT, 19 returned from hell along with several other dead villains. He was killed when Trunks and Goten blew him up with an energy blast into the alley, again leaving only his severed head.
Android 19's powers are similar to the other androids. He is able to fly, generate energy based attacks, and absorb power levels with the red orbs on his palms.