Gohan
Gohan is the first son of Goku and Chi-Chi. His brother, of course, is Goten.
The Saiyan Saga is his first appearence, with an age of 4.
Oozaru (only as a child)
Super Saiyan
Full Power Super Saiyan
Super Saiyan 2
Mystic Gohan [Potential Unlocked via Elder Kai]
Gohan Fights Frieza in the Saiyaman Saga