Goku

The Saiyan Goku, born Kakarot, is the main protaganist of the Dragon Ball/Z/GT franchise. Goku is the leader of the Z Fighters, he's appeared in almost every Dragon Ball Video Game to date.

Name Pun
Like all Saiyans Goku's birthname (Kakarot) is a pun on a vegtable, in this case a carrot.

Personality
Goku is honest and good natured and fights to win, but not to kill his opponent, this at times gets him into trouble. Goku also fighting fairly which is shown many times, such as when he threw Cell a Senzu Bean, during the Cell Games saga to recover him to full strengh, moments before his fight against the young Super Saiyan Gohan, as well as when he refuses to use Kibito Kai's Potara Earrings to fuse with Vegeta to fight the considerably powerful monster, Majin Buu, as he states it wouldn't be fair because Buu hadn't absorbed anybody in his orginal form.

Power Level
Below is a list of official power levels during Goku's life.

2 - In his birth chamber on Plannet Vegeta

10 - During his first appearamce in the early Dragon Ball

100 - Shortly after transforming into a Great Ape inside Emperor Pilaf's Palace

180 - During the 22nd World Martial Arts Tournament

260 - After drinking the Ultra Divine Water and facing the younger Demon King Piccolo

334 - Read from Raditz Scouter when Goku is approaching during Dragon Ball Z

330 - About to fight Raditz

416 - After removing his weighted clothing

5,000 - Approaching Nappa and Vegeta, read from Vegeta's Scouter

8,000 - When powering up to battle Vegeta

Over 9,000 - Still powering up to fight Vegeta

16,000 - When using Kaioken x2 against Vegeta

21,000 - When using Kaioken x3 against Vegeta

34,000 - When using Kaioken x4 against Vegeta

90,000 - After training under 100x Earth's normal gravity

5,000 - When surpressing his power on his first landing on Namek, stated by Burter

3,000,000 - After gaining a Zenkai from recovering from his battle with Captain Ginyu, he fights Frieza's final form with this

30,000,000 - After using Kaioken x10 to battle Frieza

60,000,000 - After using Kaioken x20 to battle Frieza

150,000,000 - After first becoming a Super Saiyan 30,000 - Read by Turles Scouter during the movie Dragon Ball Z: The Tree of Might

Power Levels are no longer recorder or stated after the Frieza Saga, likely due to Scouters no longer being used.

Great Ape/Oozoru
Like all Saiyan's Goku will turn into a "Giant Gorilla" if he stares at the full Moon, it can be reversed if the tail is cut off.

Super Saiyan
Goku first becomes a Super Saiyan

Ultra Super Saiyan
Goku only took on this form while training with Gohan in the Hypobolic Time Chamber at Kame's Lookout. He becomes fully aware that although the form has an enourmas amount of streng, the bulky muscles slow down the fighter considerably. Goku has only used this form once and never durin g a battle. Ironically, Goku uses this while Trunks is fighting a losing battle against Perfect Cell in this very form as he wasn't aware of its huge drawback.

Full Power Super Saiyan
Goku achieved this state after training with Gohan in the Hypobolic Time Chamber. It is a state of mental as well as physical control of the Super Saiyan. Via remaining transformed for extended periords of time one can reduce the amount of Ki used to sustain the form and store it when attacking their foes and therfore have access to an increased amount of power.

Trivia

 * Goku has achieved every Super Saiyan transformation minus the Legendary Super Saiyan form which is genetic exclusive.
 * Goku has never been the first to face any of the three major villians (Frieza = Nail, Cell = Piccolo, Buu = Gohan).