Xion

Xion is number 14 of Organization XIII. She is not a Nobody but is a replica of Roxas but took Kairi's looks from Sora's memories.

Weapon
Xion can use the keyblade because she is a replica of Roxas who can use it because he is Sora's Nobody and Sora can wield the Keyblade.

Kingdom Hearts 358/2 Days
She is a playable character in Kingdom Hearts 358/2 Days.

Kingdom Hearts 358/2 Days is the only Game Xion features in.

She is called 'Poppet' by Xigbar which is similar to 'Puppet' which Saix and Xemnas call her it is probable the Xigbar knows that Xion's a replica.