The same bit was used in an episode of Sledge Hammer called “Witless.”
Wow. That’s 8 minutes of my life I’ll never get back!
As others have posted, breaking a glass bottle by just striking it against a surface to create a weapon is difficult and unreliable. Glass, being an amorphous solid, doesn’t have any preferred direction to break and will tend to form cracks in any old direction that integral stresses or shear planes exist. What this means is that if you strike the bottle on a surface, a crack might just as easily run up the length of the bottle as around the circumference. There are ways to controllably break a glass bottle–chill the bottle and wrap a heated wire around it; score the bottle with a glass cutter and tap it with a hammer; heat the bottle and dip the end in cold water–but you can still get longitudinal cracks. (BTW, the ullage cone in the bottom of a wine bottle makes a pretty good form for shaped explosive charges; you just have to scrape out the tip of the cone to get a nice concentrated force wave.)
Barfight scenes in movies where the bottle is broken use pre-scored sugar glass. Like most things you see in films and on the televisor it is completely unrealistic; the best weapon in a bar is a heavy mug or a pool ball. A broken beer bottle really makes a terrible weapon, capable of inflicting impressive surface wounds but incapable of penetrating more than a couple of inches or applying enough force to reliably cut blood vessels or tendons. If somebody cut me with a bottle I’d slap him upside the head, take the bottle away from him, and proceed to shove it in some bodily orifice of the previous wielder.
Stranger
Well if you just want to break off the bottom of the beer bottle, there is a reatively simple, yet impressive way to do this. It takes a little time and preparation, so it’s pretty useless in a barfight, but might win you a bar bet (although it’ll probably get you kicked out of the bar).
Take a standard beer bottle, the ones with a well-defined shoulder work best, and fill it with water (don’t waste the beer) to roughly halfway between the shoulder and the top of the bottle, like you’d just taken a couple of swigs from it. Hold the bottle tightly by the neck in your left hand and strike sharply straight down on the top of of the bottle with your right palm. Hold your palm flat so as to trap and compress air in the bottle. If you do this wrong, you will look stupid and have a sore palm. If you do it right, the bottom of the bottle will pop more or less cleanly off - and you’ll have a sore palm.
Oh, and sometimes, instead of the bottom coming off, the whole bottle sort of explodes, so don’t try this one at home, kids.
If you have enough of an advantage over your opponent that you could do all that, then he didn’t have a chance with or without bottle.
I don’t think I believe this in the slightest. Air is compressible, and beer bottles are built to withstand internal pressure from a carbonated beverage. I highly doubt that the tiny bit of pressure this would produce would cause the bottle to fail. If you saw someone do this, I’d have to believe the bottle was pre-scored or otherwise rigged in advance.
Well, that’s kinda the point. Anybody who thinks having a bit of broken glass in his hand is going to give him a substantial advantage is probably deluded and soon to be removed from this world. All you’re going to do with a broken bottle is inflict superficial cuts, and all that will do to a serious opponent is piss him off.
Strnager
No, he’s right about this, although it will take a certain amount of practice to get this to work consistently. The pressure in a bottle from carbonation is typically <1 psi, hence why the cap doesn’t pop off energetically they way it does with sparkling wine. By doing as the poster suggests you can get ~20 psi in a pulse. Even after transient compression losses in the small amount of air in the top of the bottle (and it must be a small amount, less than 1/4") and expansion of the wave in the main part of the bottle, you can transfer enough force to the base of the bottle to overstress the edge where the bottom meets the size, and the bottom pops more-or-less cleanly away. For this reason the minimum amount of ullage in glass and aluminum beverage containers is tightly controlled as otherwise a slight amount of external force can cause overpressure and failure.
This works best with cheap American beer bottles that are as thin-walled as possible; I don’t think you could get away with this with a bottle of Bass.
Stranger
So, how’s the weather in Glasgow this time of year ? 
If you actually want cleanly to remove the bottom of a bottle, I learned a trick that allows this.
Put a heavy-ish kitchen knife into the bottle and shake it around like crazy for about two minutes. Then tip the knife out, and, holding the bottle over the sink, drop a long, thin heavy-ish item (like the same knife) into the middle of the bottle’s bottom. Usually, the bottom of the bottle drops straight out as a disk, the edge of it having been weakened by the bumping of the knife.
Stranger on a Train has already answered this quite well. I just want to add that I believe it’s possible because I’ve done it. Makes a hell of a mess.
Another quick and easy way is to get some wire, wrap it tightly around the base, then plunge the bottle into an ice bucket. The wire will contract more than the glass and cut the bottom off the bottle. It works even better if you warm the wire up beforehand.
I have too, and after 23 posts, I thought I was going to be be the first to post it. Damn you, Rhubarb ::shakes fist:: Just as well, really-I couldn’t remember the proper air/fluid ratio because I was just as drunk as you’d expect when I saw this particular light.
Kentucky, Missouri, Montana?