The Blast Box (爆薬箱), is a heavy item that appears in Super Smash Flash 2. It is notably the only explosive-type item in the game.
The appearance of the Blast Box is that of a wooden crate with a fire hazard warning label pasted in the front of it. The crate can be hit multiple times before it explodes while it will explode instantly when hit by a flame attack. When hit, it will slide across the stage. When a character is hit by the explosion, they will receive a ton of knockback.