Battle on Planet Namek
Majin Buu conflict
The Grand Tour Conflict
Z Fighters (Z戦士, zetto senshi, also known as the Z Warriors or Earth's Special Forces) are a small group of super warriors located on Earth. Their duty is to defend Earth from major threats and to protect the seven mystical Dragon Balls from the hands of evil. The Z fighters are not officially organized in any way, because it is simply a group of super fighters who all share the same interest of protecting their home. However, they all stand together whenever possible to fight off enemies. Goku is the de facto leader of the group due to his incredible success rates against villains in Dragon Ball, victory over the Saiyans, and his victory over Frieza (Krillin even mentioned in the episode "Upgrade to Super Saiyan" that Goku was in command).Piccolo and Goku kicked of the formation of the Z Fighters.
During the Dragon Ball anime, a similar team existed, but it was called the Dragon Ball Gang. Their original purpose for coming together was not to protect the Dragon Balls, but to use them themselves. Later, however, the members of the Turtle Hermit School trained by Master Roshi, would join together to combat evils such as Emperor Pilaf, the Red Ribbon Army, and King Piccolo, thus this team could be considered an early rendition of the Z Fighters. Its main members consisted of Goku, Krillin, Yamcha, Tien Shinhan, Chiaotzu, Yajirobe and their supporters.
The first actual formation of the Z Fighters was out of necessity, brought on when Goku was faced with Raditz, who had kidnapped his young son Gohan, and wanted to destroy the Earth. Goku formed an alliance with his arch rival Piccolo in order to fight for a common cause. The alliance made from necessity is considered the true birth of the Z Fighters.
Trunks – Vegeta's only son. He is a Saiyan/Human hybrid.
Goten – The second and last son of Goku, whose appearance closely resembles his father's. He is a Saiyan/Human hybrid.
Krillin – A human, he is Goku's best friend and former schoolmate. He has the distinction of being the only human to stay on the "team" after the Cell Games, as Yamcha, Tien, and Chiaotzu all retire. He retired in GT.
Yamcha – A human, once a fearsome desert bandit. Chronologically, he is Goku's first fighting ally. Also retired in GT, and one of the first to be in the group.
Tien Shinhan – A human with a third eye who has hit a peak of enlightenment. He is a former assassin and Goku's former rival. He also retires in GT, although he continues to train, unlike Krillin and Yamcha.
Chiaotzu – A human who excels in psychic abilities. He is Tien's best friend and former schoolmate. His last fight on the team is against Nappa, as Tien says that Chiaotzu "just can't keep up".
Yajirobe – A human samurai who never really wants to help Goku and the rest of the Z Fighters unless there is food involved. Though, he does help the Z Warriors by delivering senzu beans from Korin. He also played a big part in defeating Vegeta by cutting off his tail.
Uub – A human reincarnation of the enemy Kid Buu, he becomes Goku's pupil at the end of the Dragon Ball Z series.
Future Trunks – The time-traveling version of Trunks from a devastated future. He is a Saiyan/Human hybrid.
Future Gohan – The bleak future version of Gohan who is the sole survivor of the original Z Team. He is a Saiyan/Human hybrid.