I love swords. They just have so much style and character. To appropriate a quote from Jedi Master Obi-Wan Kenobi, They're an "elegant weapon for a more civilized age". Or at least that's how I like to think of them anyway.
The problem with swords is that they can get expensive and they're not exactly "safe" to carry around everywhere, which is a problem if you've decided to dress up for Halloween or a similar event and you're character has a sword. Many conventions don't allow real swords (or even hard wooden swords) and when trick or treating or going to a costume party the more responsible option is a fake sword (especially if there will be drinking at the party).
So, what do you do if the character you're dressing as has a very specific weapon and there are no toy versions available commercially or it's too expensive?
You make it out of foam board of course!