Fire Arrow

Ocarina of Time
The Fire Arrow is an upgrade to Link's bow arsenal. It causes the spot it hits to burst into flame. This attribute makes it quite useful for lighting torches, melting ice, dealing significant damage to enemies and etc. They are particularly useful when there are torches that Din's Fire would be useless for because they were too far way. You can get them by going to Lake Hylia, standing in front of a stone with writing on it (above the Water Temple entrance), and shooting an arrow at the sun. It will drop down and you will obtain the fire arrows.

NOTE: They can only be obtained after beating the Water Temple. There is a small ledge where Navi can turn green, but this is not a a scarecrow spot.

Majora's Mask
They are more useful in Majora's Mask than in their first game, Ocarina of Time, particularly against the boss Goht. They're acquired in the Snowhead Temple in Majora's Mask.

The Wind Waker
You get this in The Wind Waker at the Mother and Child Isles after receiving the Ballad of the Gales. Just warp and you've got it.

NOTE: To get the Fire Arrows you must beat the Forsaken Fortress a second time for the 'Doors of your destiny to swing open'.

Twilight Princess
The Fire Arrows are not obtained in the normal game flow of Twilight Princess. However, item number 53 is named "Fire Arrow" meaning that they were originally meant to be obtainable. The Fire Arrows are still used but by enemies; Bulblin Archers use them against Link, which can cause problems for his wooden shields.