English: Krillin
Japanese: Kuririn

Krillin is considered to be the most powerful human on Dragon Ball (although, I think Tien can give him a run for his money, provided you count a triclops as human). He's the short, self-conscious, wise-cracking "side-kick" of sorts, hanging around Goku like the two are joined at the hip. But they grew up together, and the friendship that blossomed between them remains one of the strongest bonds throughout Dragon Ball.

Krillin and Goku trained together under Master Roshi, learning the lost-art of ki-manipulation from the centuries-old hermit. They withstood very demanding training, and endured many dangerous adventures... and through these experiences they became brothers.

As with all non-Saiyan characters, the further into Dragon Ball Z one goes, the less Krillin is able to contribute to the battle. Still, he was the only human to survive the fight against Nappa long enough for Goku to intervene, and he helped Goku launch the Spirit Bomb that lead to Vegeta's defeat. Also, he accompanied Bulma and Gohan to Namek, fighting ki-warriors that vastly outclassed him, but always taking bone-shattering kicks with a lop-sided grin.

Probably the biggest contribution Krillin made was in his death, and it gave testament to just how close he and Goku were. Frieza mercilessly caused Krillin to combust, and the gory death of his best friend is the singular event that pushed Goku through the roof of his power, straight to Super Saiyan.

Not only was Krillin a close friend of Goku's, but he also kept his eye on Gohan during Goku's continual absences. Gohan and Krillin become close friends in their own right, but Gohan never forgot to view the oft-silly monk with respect.

Krillin is also notorious for his girl problems. It seemed his greatest fear was growing old alone, and he couldn't surmount his low self-esteem enough to actually believe a woman could honestly love him. But he eventually found his match... in Juuhachigou, or Android Eighteen. Unlike everyone else, who saw her as an evil creation of destruction, Krillin saw a beautiful young woman who was victimized by Doctor Gero. She was a cyborg, not an android, meaning that deep down she was just as human as he was. And his patience, consideration, and faith in her eventually won her over. And Krillin left his life as a monk behind, grew out his hair, traded his gi for cargo shorts, and lived happily as Juuhachigou's husband, and Marron's father. However, despite his retirement from the Z-Senshi, his friendship with Goku and his old comrades never faded. He was always prepared to join them in the latest adventure, looking to assist his childhood friends whenever possible.