This sleek, space-age stainless steel take on a saber from Menu is proof that a champagne saber doesn't need to be sharp to get the job done. It's the impact that matters, after all, not the sharpness of the blade.
The fine art of sabrage -- the fancy French term for opening a champagne bottle with a blunt sword rather than the standard humdrum method of just popping the cork -- purportedly gained popularity during the reign of Napoleon. His conquering cavalry would slice open bottles with their sabers to celebrate their many victories. These days it's the job of well-trained sommeliers, although the ready availability of tools like the saber pictured above is making sabrage more popular among amateurs.
You want a French bottle of champagne, if possible, since the glass bottles tend to be thicker, the better to contain all that pressure (about 90 psi pushing against an opening less than an inch in diameter). The key is to strike right at the lip, where there is a seam that concentrates all the stress from that pressure on the bottle -- the weakest point. Hit it just right with the end of a saber, and you make a crack that quickly spreads through the glass, severing the top from the bottle. (Helpful hint: don't point the tip of the bottle at yourself or any party guests. It can fly as far as 9 metres when it finally pops.)