Originally Posted by Mercen-X
Think logically. Sora and Roxas were unable to battle heartless with the wooden sword and the Struggle weapons, why? Because they were not strong of heart . . . yet. The Keyblade is Sora/Roxas' symbol of heart. When they became strong of heart, the Keyblade appeared. The other characters (i.e. Donald and Goofy) don't need a Keyblade because their hearts are strong enough to battle the Heartless and the Nobodies without it. That's why Tifa can battle them without any weapon.