This blaster idea is probably the most similar to the ones we see in the movies. In theory, a "bolt" of plasma would be generated (likely from a high-pressure gas container) and then shot out just like the projectile in a coilgun. The plasma would of course have a charge, so it would theoretically be attracted to the coils and gain enough momentum to shoot out with a decent amount of velocity.

The problem with this idea, however, is that the plasma would likely dissipate quickly in the atmosphere. Also, plasma constantly "wants" to return to its normal state (in this case, gas). That's actually why it glows -- it releases the extra energy as photons. So unless one could find a way to keep feeding it energy, it would lose its energy and dissolve into the atmosphere at a certain distance away. This distance may be increased, however, by increasing the speed at which it leaves the gun (that's my guess anyway).

As always, contact me if you have any suggestions!