Navi

Navi is Link's guardian fairy in Ocarina of Time. A lot of fans consider her annoying and useless, but she seems to be overlooked by many.

In the game, the Great Deku Tree summons her to his side after Ganondorf cursed him for the Kokiri Emerald, and she soon meets Link. She wakes him up and she sticks with him throughout his adventures, even when he grows up seven years later. She's been very helpful on pointing out enemies' weaknesses, as well as targeting and reminding him on his objectives. She stays as a valuable companion until his adventure is over after he defeated Ganondorf and returned to the past. She flies away, never to be seen again, not even when Link was looking for her in Majora's Mask.

Ikran's Lost Pokémon/OoT crossover
Navi's still very helpful during the adventure, but not quite as annoying as people think. At one point, she has been contained inside a bottle when Link was being brainwashed by the Gerudo. She still stays with Link, Zelda II, and her Pokémon throughout the journey centering on the Hero of Time.