Piece of Heart

A classic Zelda item. Four Pieces of Heart are required to form one Heart Container in most games. Pieces of Heart are scattered all across Hyrule and the other game loactions. Link can usually aquire a Piece of Heart by completing a task for an NPC, reaching a difficult part of the terrain to get to, or through many other means.

A Link to the Past

 * ZeldaUniverse.net's Guide
 * Karri Huismann's Guide

Ocarina of Time

 * ZeldaDungeon.net's Guide

The Wind Waker

 * ZeldaUniverse.net's Guide

Other games

 * Super Smash Bros.
 * Super Smash Bros. Melee