I've been playing around a bit with Balisong pens, err... I mean knives... totally... anyways, I was playing around with one and thought, "what if this was sword sized?" I decided it would be cool and drew one up. Then I did some research and found out that this sort of thing apparently really exists. That sort of ruined the fun, but for the record, I did think of it before I knew about its actual existence.
It works just like a balisong does, just bigger. Obviously the tricks and openings would have to be modified for one that's nearly 3 feet long, but I think it would be fun to play with.