If you're going to sculpt your own, I advise doing the handle/hilt separately from the blade and then gluing the two parts together. Blades can be fashioned out of almost any thin material, be it metal, plastic, wood, etc. Draw out the shape you want, attach it the material in some fashion, cut it out, and then hone the edges or whatever you want to do with it. Remember to include a small piece sticking out at the bottom of the blade that you can use to firmly attach to the handle (I usually do a peg/hole type arrangement). For the handle, I'd start with a tube of some type (preferably hollow if you're going to do the peg blade attachment approach I just mentioned) and then embellish that basic shape with whatever you want.
You can do the whole thing as one piece too, depending on the type of weapon you're trying to do and your level of skill.
Look at one of my deadpools in the realm, it has metal swords in the title. I gave some instruction there. I'm on my iPod touch so I can't post a link.
what do you want to make them out of? My dad made me a pair of FF7 buster swords from steel in our forge (we make real swords/knives) that are letter openers. You can resin cast them from premade swords, you can make them out of sheet styrene like you use in model kits, you can even use aluminum from a home improvement store.
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You can do the whole thing as one piece too, depending on the type of weapon you're trying to do and your level of skill.