X is for X-Shaped Jewel, a treasure from Oracle of Seasons that - when used in conjunction with the Pyramid, Round, and Square Jewels - lets one enter the Tarm Ruins.
E is for the Earth God's Lyric, a song featured in The Wind Waker. It is a song that, when played in Medli's presence, awakens her as the new Earth Sage.
G is for Gubora who, along with his buddy(?) Zubora, is a blacksmith who lives in the Mountain Village, a location in Majora's Mask. He and his partner can make Link's sword "very powerful" with the help of a special substance called Gold Dust. Oh I forgot to mention he is very big...