The kids got a cheap plastic sword with their Halloween costumes last year. They eventually broke it so I made them both new, better ones. Modeled loosely off a real greatsword hanging above my desk.

The blade slots right into the grip and I used a few dots of gel superglue to hold them in place. After a month or so of the kids sword fighting I've yet to have one come undone.

NOTE: I am not liable if your child injures himself or herself using this design!