The Balance Point
This is a term known mostly to fencers and blade enthusiasts; however, I'm going to make a genuine effort to bring it into your living room. The balance point a.k.a. the center of gravity of a weapon (usually a sword, although theoretically it could be any kind of weapon I suppose) is the part of the blade that, if you were to place it upon something, the weapon would balance. Just like magic, you see; however, it is not to be confused with the percussion point, which is something entirely different.
On most weapons of a 'normal' size, this is found only a few inches from the handle/pommel. There are, of course, exceptions given for size, such as zot-fot-piq's Claymore. These exceptions to the rule are what made the use of such large swords uncommon. Certainly you would never want to use a sword with a balance point farther than 7-8" out from the handle for any sort of finesse attack, it would simply be too difficult for any normal person to handle.
If you wanted to see a direct example of a balance point and didn't happen to own a sword (unlucky you), you could watch any of the following movies: Willow, Dragonheart, or 13th Warrior, and if one watches closely when the warriors choose to reverse their grips or throw their swords (be it the case), you will notice there is a part of the blade a few inches from the handle that doesn't seem to move that much. This is most noticeable in Madmartigan (Val Kilmer), but if I remember correctly you can see it well enough with Bowen (Dennis Quaid) during the section where he is using a twin sword style. If you wish to see the balance point on Ebin's (Antonio Banderas) sword, you can really only see it directly after he is finished creating it. At any rate, the part that doesn't seem to move much is the balance point, and in fact, assuming that the movement was performed perfectly, the balance point itself would move only in a perfect circle.
Now you've learned your fencing term for the week, so go stab, slash, and kill stuff.