I was thinking about how in every major image of Sora with a Keyblade, it's almost always the Kingdom Key. Granted it's probably because it's the simplest to illustrate but I wanted to put a little sentimentality behind it…
I do not in any way, shape or form own any aspects of Kingdom Hearts. They all belong to Square Enix, Disney, and Tetsuya Nomura respectively
The Kingdom Key
One warm day in Radiant Garden, Sora sat on the steps outside Merlin's home, cleaning out his infinite supply of items and paraphernalia he had gathered along his journey. Yuffie, exploded from the house waving around a Sea-Salt ice cream bar, a maniacal grin playing around her mouth. She stopped, mid step at the sparkling array of Keychains Sora had laid out on the step just beneath his feet.
"Ooh, Spiky whatcha doing with all these? Wanna lend any to me?"
Sora laughed and shook his head, pulling out another one from a pocket of his pants. "Ah, Donald was complaining about how heavy the pack had been getting so I decided to clean out all the stuff we didn't really need anymore."
Placing the green chain of Rumbling Rose beside Yuffie, Sora continued to reorganize. He tossed out old synthesizer items and threw away empty Ether and Hi- Potion bottles.
"Hey Spiky, if you're got all these awesome weapons right here, why do you always use the gold and silver one?" Yuffie questioned, fiddling with the chrome and wolf crest of Fenrir.
The question gave Sora pause, his own hands twisting the crowns of his Ultima Keychain. Yuffie had a point, the brunette wielder thought. The Kingdom Key was his most basic weapon, the others he had gathered had more offensive, defensive and tactical advantages. He summoned the weapon, its gleaming steel and shining guard as familiar as his crown necklace. His Kingdom Key was the first Keyblade he had ever received, that fateful night he and his friends had been tossed into their paths. It had been the weapon he had taken down so many Heartless, fought against Riku and Ansem and rescued Kairi with. The blade had been useful when Hollow Bastion had been overtaken by the Heartless and Organization XIII. It had taken down nine Organization members and unlocked the Door to Light, locked the Door to Darkness and brought everything back together, he and his friends reunited and home.
So, scooping up all the keychains and putting them into a special pocket of his bag, Sora responded to the hyper ninja, sky blue eyes twinkling. "I guess it's because of all the memories."