How do you get the x-blade in Kingdom Hearts Birth by Sleep?

Answer 1

Synch blade is not a obtainable ability in Kingdom Hearts 2.You can only use Synch Blade while in Valor Form, Master Form, and Final Form.
Synch Blade, is an ability only available to Valor, Master and Final Form. You can however find a cheat code from GameShark, Codebreakers or Action Replay MAX, that will allow to get two blades.
you cant get synch blade for normal sora the only time you can use it is when either your in a drive or when you fight axel as roxas at the begining of the game,so unless you have final mix + then im sorry to say that you cant. p.s to get in final mix you have to get level 99 when you choose the staff shaped struggle sword and in dive to heart use the shield

Answer 2

You can't get the gunblade ._. You can get a keychain from Leon though

The keychain from Leon gives you the gunblade.

Answer 3

I don't think there is a way to actually get it without using something like action replay or gameshark