WHERE THE FUCK DID YOU GET A LASER GUN? 
(SEND ME ONE!)

All right space cadet, the author is not sure what kind of hardware you expect to have at your fingertips, and isn’t going to ask.  It may be best to address the topic of bringing a laser to bear as a hand weapon in two parts: hardware you’re likely to get your hands on (circa 2009), and a few ideas on using it. 

 

For simplicity’s sake, we’ll assume you have are dealing with a handgun styled setup, not a laser rifle, for reasons to be covered later.
Lasers are NOT effective handheld weapons currently.  Most commonly available lasers are a fancy way to make a red dot appear somewhere, and can’t do much more than blind someone briefly when they hit they eyes just right.  You can acquire models that will light a cigarette or burn plastic bags, but these would need long exposure on unprotected flesh to cause even minor burns.  Nothing with the power (equivalent to a firearm) has been developed into a handheld, much less man – portable, weapon just yet.  Weaponized versions are still confined to trucks or airplanes specially designed for the purpose, and require great resources to operate.  There are a few “less lethal” concepts that use lasers or other pulsating light to cause nausea, but they require a very different setup than a burning, cutting laser. 

It should also be mentioned, a laser is not an all trumping cutting / blasting tool.  A laser only makes things hot, by applying a lot of light to a very small point.  (Or a wider area when unfocused.)  They apply no force, and as such will blow nothing apart on their own.  Even with a very powerful laser, it takes the beam time on an exact point to heat the target enough to damage it.  For the time being, the best a laser could hope to do is damage by heat a target that will hold still long enough for it, or be tracked very accurately long enough, for this burning to happen.  Easy with an arrangement in a large jet or truck, but not exactly practical for a handheld model.

 
An actual “light fight”, to steal the term from science fiction, to the author’s knowledge, has yet to happen with fatalities.  (Heart attacks playing laser tag notwithstanding.)  The author is no gunfighter, and skill with a pistol may be one of the closest ideas to use of a handheld laser gun.  The basic idea, assuming a laser of sufficient strength to burn through a clothed human in 0.1 or less seconds, would be the same.  The dangerous area involved with the weapon would be a straight line out from the tip of the barrel when the trigger is pulled.  Unlike a gun, however, the laser would not involve a projectile, and would be dangerous as long as the trigger was held down.  No appreciable recoil either.  Imagine a rapier of indeterminate length that cannot be parried or blocked, has a blade that weighs practically nothing, and is sharp in every direction at once.   That’s basically what you have to defend against, or be offensive with.  Like with guns, the golden rule is “Don’t be in front of them”.  Outside of arm’s reach, you can be dead as quick as the opponent can draw a bead and pull the trigger.  Given the nature of the laser though, they can decide to “swish” the beam THROUGH you if they don’t target you right on the initial activation.  Inside arms reach techniques for defending against a handgun also work, as far as using your hands and body to get the tip of the barrel pointed away from you.  (In fact this may be easier, as you don’t have to worry about blinding from muzzle flash, deafening, powder burns or laceration from moving parts if it goes off right next to your head.)  At range though, find cover and keep moving.  Make sure it’s something that takes awhile to burn through too.  Mirrored shields would only be a temporary solution (No reflector being perfect, it would only be a temporary solution at best.) 

If you both have laser weapons, use yours first.  (This is the simple way out of any fight, armed or not.)  If you can’t then keep your head down, keep covered, and try to flank or lure the other guy out.  Trading fire is leaving things up to chance, and getting pinned down limit options fast, especially if they can burn up your cover.  If you both end up at arm’s length with laser pistols, then something’s really wrong.  Refer to Kurt Wimmer movies, and pray you have time after to wonder how you got into such a stupid fix.