Valve Software came out recently with the game, “Portal.” In this game, the player runs the victim of an unfortunate science experiment through a series of puzzles involving the ability to open pairs of portals (one blue, one red). These are, effectively, a portable hole. Things that go in one portal come out the other. Because momentum is unaffected, a number of the puzzles involve you throwing yourself off of a high place, falling through a portal on the ground, and then ejecting yourself at high velocity at the conveniently placed other end of the portal.
Free Kinetic Energy The basic way in which portal technology is used in Portal is to move matter from place to place. Apart from conquering distance and re-directing energy balls, the obvious direction to go is straight down, the infinite elevator shaft. This makes use of the earth’s gravity to get free kinetic energy. In Portal you mostly just fling yourself about with it, but this kinetic energy could be used in several ways. Try placing a magnet in a vertical tube and coiling wire around the tube. With the portals added it becomes linear generator! Strap some mass to the magnet and evacuate the air. Now the generator will charge up kinetic energy when there is no power being used. A more military application is the kinetic energy weapon. Evacuate the tube and throw some long rods into it (or ball bearings, old washing-machines, whatever). With the air resistance gone any object in the tube will reach fantastic speeds. In just eight hours it will have exceeded 9/10 of the speed of light! Redirect it through a portal for a nuclear-style explosion. You could launch stuff into space this way too. Of course, once you launched a portal (or the associated generator) into space you wouldn't need to launch anything else.
Oh, and the game is fun too. I’ve played through it a couple of times and unlocked the bonus levels. I just wish there were more maps available.