Even if it's confirmed that we get to fight Zexion, I don't think it necessarily means that he has a weapon. There's a reason why in the one 3d scan of the COM unknowns all standing side by side that Zexion had his arms folded without a weapon, and why he didn't have a weapon on his tombstone. And I doubt it was out of Nomura's laziness to create another weapon or a loss of ideas for creating another weapon. There's also a reason why he couldn't defend himself from Axel/Riku; he doesn't have a weapon. I think his "weapon" is strictly mental energy. Or shooting some sort of dark/gravitational(I already forgot which unknown is in charge of gravity. Wasn't it Xigbar?) force at the opponent using his hand. Remember his signature pose of flaunting his hand dramatically at the opponent, reminiscent of Yugi's mind crush? When playing CoM, I thought the only thing he was good for was to send the opponent into a strictly illusionary world/ transform into other people. I doubt it would be much use if he could transform into other people and not know how to use their attacks. But then again, it'd also be fun if he transformed into a random unknown or Riku at any given moment, and then you'd have to switch your strategy. Wasn't Zexion the leader of the basement? It'd make sense if he was that hard to beat then. I seriously doubt his real weapon would end up being sending people into an illusionary world since there's almost no real way of making that in such a way where Zexion is opposable. Unless they turned the stage into some sort of Legend of Zelda-like set-up, where you'd have to avoid lava or jump over certain platforms to finally get to the boss. Maybe Zexion has telepathy and throws objects at you? Who knows? I've exhausted all my ideas for now.