Do you get a keyblade after you beat sepiroth in kingdom hearts 2?

Yes you do. It's called Fenrir. After you beat Sepiroth you go talk to Cloud and then go back to where you fight Sepiroth and a cut scene will play.(I won't spoil it). Tifa will give fenrir to you after the cutscene. Some people think that Fenrir is better than Ultima, but it just depends on how you fight.