The way I figure...
I can get pretty obsessive over completing games I play to 100%, especially Zelda games. Heart Pieces, Gold Skulltulas, rings, hidden items. I feel I haven't given a game the attention it deserves unless I have
completed the checklist of things to do and experienced everything the game has
to offer. Wind Waker's figurine collection, known as the Nintendo Gallery in the game, sparked up my inner completionist in a way that had never been done in a Zelda game before. Beware, if you're only experiencing this game for the first time on your Wii U, there might be some minor spoilers ahead!
At the time this game came out I was in university learning how to make and animate 3D CGI models. This only amplified my desire to finish the Nintendo Gallery. 3D models of every character, enemy and creature in the game? Yes! 360 degree rotation and zoom, allowing you to see how they looked from different angles? Heck yes! Something like this was perfect for someone studying the art of polygon crafting and, given my obsession with collecting figurines to start with, it was the coolest sidequest ever.

The way in which you obtained these figurines was a lot of fun. Partway into the game you're given the chance to get an old Pictograph Box, a black and white camera to carry around with you. If you manage to find the hidden location of the Nintendo Gallery, Carlov, the owner, will offer to sculpt figurines of anyone you snap a photo of, but only if you're able to obtain color photos. You must then complete a relatively convoluted photography sidequest to upgrade the camera. Even after you complete your objectives and the quest begins, the photos you hand over to the sculptor must show the subject's entire body, centered in the photo's frame, and they must be looking at the camera. To top it off, the camera was only able to hold three photos at once, so you had to carefully prioritize which photos to keep. It was such a massive challenge, but to me the outcome was so worth it. There was even a special hidden figure that could only be obtained by completing the (almost as awesome) Tingle Tuner sidequest with your GBA connected to your GameCube, and one last figurine that would be awarded to you for collecting every other character in the entire gallery.
My only gripe was that by the time you usually finished the necessary quests to be able to start your collection you had already beaten the first few dungeons and missed some one-shot opportunities to snap your photos. Fortunately your figurine gallery and possession of the Pictograph Box carried over to a new quest when you completed the game, allowing you to go back and get the figures you missed. Unfortunately, from the second time you start a new play-through on your old save file, Link wears a different outfit. I don't know why this bothered me so much, to this day I can't fully explain my frustration, only that in my mind Link's alternate costume was the ultimate badge of failure. My meagre skills were so pitiful that I had to resort to starting the whole game over in order to finish one quest. It taunted me. It pushed me over the edge of excessive determination and into obsessive compulsion. I resolved to do the impossible.
I completed the entire figurine collection in a first-run play-through of the game. This monumental task required constant planning and hours of hard work. In order to obtain the upgraded Pictograph Box as early as possible I had to break the sequence of events of the game, backtracking from the Forest Haven to Windfall Island while detouring past Dragon Roost island, traveling against the wind direction (which at that point was forced south) and only moving in sections of the map that I had been allowed to travel so far. Up until a certain point, the King of Red Lions would force Link to stop and turn around if he tried to sail off the edge of certain map segments. I had to continually leave a dungeon halfway through so I could get some figurines made, so that I would have the required slots in my film when it came time to battle the boss. I even had to save and quit during the final battle in order to get suitable pictures of Ganondorf.

Photographic proof! Link stands by the final figurine in his normal outfit.
What did all that effort net me? Satisfaction and bragging rights that I could proudly look upon my completed collection with Link dolled up in his Hero of Legend garments, and not much else. At the time, strategy guides claimed it was not possible to complete the task without restarting your game, and I proved them wrong. Since then specific guides on the topic have popped up around the internet. At least I can take solace in the knowledge that I'm not the only crazy one out there.