The examples given in this thread make me laugh. First of all, Light cannot be a type to just merely mimic the Dark type. We already have Fire and Electric to create an image of Light (more of the Electric type though). Unless you are aiming for the impression of "holiness" with the word light, but you'd need a better word for it. Sound is probably the better ones you can think of, but it is quite silly though. Anything can make sound, why do we need a specific type for it? They really fall under the Normal category. Plasma falls under electric, undoubtedly. Crystal is taking the image of a gem or some crystalline figure that is hard and transparent. Ice is really another name for crystal. Also, there is a version called Crystal for the Pokemon Games, so getting a type named after a version would be quite silly. Magnetism is the force which bonds two objects together. Even so, we already have Magnemite and Magneton, which already got their types changed once. Getting their types changed again will be seeming quite redundant. Besides, a child merely thinks about Magnetism as Electric and Steel. Even if you approach the word Magnetism scientifically, the concept is much to narrow to be put into Pokemon. Gravity is quite silly. We already have a move called Gravity, so creating a new type based on Gravity would be quite silly. Gravity is much too narrow, too. Air is simply flying. Flying Pokemon create tornadoes by flapping their wings. Simple as that.
The best we can probably get with another new type is the Light type, although a better name is needed to withold the "Holy" idea. Another idea has come to mind about the energy flow, or chi. Some type that has to do with balance in the energy and Fung Shuei would be nice. A "Cosmic" form would be very nice to some Pokemon, like Palkia, Cresselia, Lunatone, Solrock, the Clefable line, and others.
