Sabreing a champagne bottle doesn't really require a sword -- a long chef's knife will do. While it doesn't make your bubbly taste better or pour smoother, it's a fun way to kick off a ceremony and impress your guests. If you're into the idea, the folks at Bon Appetit show you how it's done in this video.
Essentially, the keys to easy sabreing is to get a nice, cold, wide-bottomed bottle of bubbly, remove the foil and the cage around the cork, hold it near the bottom, and angle it up about 30-45 degrees. Then, put the blade against the neck of the bottle, and angle that about 45 degrees from the bottle. A dull knife works best (if for no other reason than that you don't want to damage your knife); you may even want to use the back of your knife instead of the sharp end.
Then slide the blade up along the neck of the bottle in one strong, swift motion. You're not trying to pull the cork out of the bottle so much as you'll use the force and pressure to pop the entire top of the glass off, cork and all. You can see it in slow motion above. It takes a little practice, but it's definitely impressive if you can get it right. Hit the link below to read more.
How to Saber a Champagne Bottle [Bon Appetit]