Four Xacto blades and some tape makes for a decently fun and dangerous facsimile.
Two straws from any restaurant, some cellophane tape, and a straight pin makes a pretty decent blowgun, too. The trick is to wrap the tape around the pin into a cone shape the exact diameter of the inside of the straw.
And you can make a miniature crossbow out of a bobby pin, some sewing thread, an alligator clip, and a pencil. It will shoot bolts made of matchsticks with pins taped to them.
Of all of these, the blowgun works the best.
The crossbow is pretty weak, but more interesting.