Kuririn

Goku's best friend, Kuririn is usually the comic relief.   Despite this Kuririn is an incredible fighter.  In Dragonball he is almost as strong as Goku is.  When we first meet him he's sneaky and self-centered, however, during their training under Kamesennin, he undergoes a change in personality.   Because of his small size, Kuririn is a smart fighter, and uses his head in tough situtations.  He is always there for Goku, and vice-versa.  Even though, at first he and Goku are only an inch or two apart in height as kids, Kuririn is more than a head shorter than Goku as adults.  We find out at their first Tenkaichi Budokai that Kuririn is one year older than Goku.  So at the end of Dragonball he's 19.