This will be the millionth time I've said it, but mods are a treasure. They allow folks to tweak their favorite games even if they don't have the ability to code a project from the ground up, and have given so many people joy over the past several decades. That goes double for this upcoming project "The Legend of Zelda: Ocarina of Time Online."
Yep, just as it sounds it's a mod that allows co-op play for Ocarina of Time. The project actually kicked off a while ago over at Hylian Modding, but the team just posted a video of a working prototype and it looks great. Hylian Modding is aiming to get it working for a simple two-player experience all the way up to 15 players for the full Ocarina of Time campaign.
Pretty much every Zelda, from 2D (both Four Swords games were great) to 3D could work in co-op form, even if it might not be the most ideal way to play it the first time around. I'd welcome a mod for pretty much everything, and the wildly popular Ocarina is a natural place to start.