Lightsabers exist. But the government hides everything cool. Damn.
According to this thing I was watching the other day, lightsabers are also not entirely implausible. We just lack the technology to create an isolated stream of plasma like that without a large building's worth of extremely expensive equipment. X)
Also, in Dragon Ball Online, ki control is widely acknowledged and utilized due to the release of Gohan's book, "Groundbreaking Science."
Ohoho, that science would definitely break ground. And either the lightsaber would require the equipment that you mentioned, or it would just shoot off forever, making an infinitely long saber.
Sometimes I wonder how far I have to go into these things before I'm to be classified as a complete loser geek.
For instance, how bad is it that I'm able to cite real-world science to justify humans' ability to become super saiyan in Dragon Ball Online?
We already owe them trillions of dollars anyway. What's another trillion? X)
It's just like playing StarCraft. :O
Does it have jet packs?