A large key-shaped weapon used in the Kingdom Hearts video games. Its main use, contrary to its name, is to bludgeon black people into submission. However, it can also be used to seal/unseal any lock or pathway, unless otherwise dictated by the game's developers.
Person 1: What's the thing in your hand?
Person 2: This is a Keyblade, a weapon that unlocks anything and can destroy the forces of evil.
Person 1: And all you use it for is beating up the black people?
Person 2: Pretty much. I can't get this door open though.
Person 1: Just use the 'unlock anything' power, then.
Person 2: It doesn't work like that. Duh.