The games have a recurring theme of some projectile weapon being the key to defeating Ganondorf. In Link to the Past, Link recieves the Silver Arrows from a fairy. Silver has a mythological power to slay things of great evil. Werewolves and vampires, creatures otherwise hard to kill, will fall beneath a silver bullet or blade. The same principle seems to work with the Dark Lord Ganon.
However, in the later games, Ocarina of Time and The Windwaker, the final instrument of Ganondorf's ruin are the Light Arrows, which are given to you by Princess Zelda. In the case of The Windwaker, Zelda actually shoots the arrows for Link, giving him time to attacked the stunned Ganondorf.
While silver is an agent of defeating evil, "Light" implies that the arrows are an agent of good. To be sure, light can pierce the darkness, and all the appropriate symbolism that goes along with it. At the beginning of the game, Zelda compares Link to a light coming out of the forest to part the storm of evil.
I had a dream... In the dream, dark storm clouds were billowing over the land of Hyrule... But suddenly, a ray of light shot out of the forest, parted the clouds and lit up the ground...
When Link shoots the arrows at Ganondorf and stuns the Theif Lord, the metaphor is made literal. But Zelda is an important agent of the light, and again, she is delegating the power necessary to Link to help him on his (and their) quest to rid the land of evil.
But mainly this is just another, "Ha! See, without Zelda, Link would be screwed" page.