If you mean a fully visible beam, then that's unrealistic. Only extremely powerful lasers have a visible beam, even then, the beam is only visible if dust/water/smoke/etc particles are in the air, and in the first place, no one in a life-or-death situation (apart from using IR laser as pointing device) would even want a bright line extending from their gun to the point of aim, apart from Hollywood directors.

However if you just mean visible dot, then sure, this is common enough on handguns and rifles.

However lasers are mostly for target designation and night-fighting when wearing NVGs.

Of course not fully visible beam ...

With visible lasers you can see only the dot but sometimes you can see the beam in the dust/water/smoke/etc

Here you have perfect example what i want http://www.youtube.com/watch?v=DnKLOjbuw_I#t=852

VBS2 got this looong time ago - when BIS borrowed the IR laser feature from vbs2 , i thought they could use whole feature of the vbs2 laser

btw US army or Marines are using visible laser devices during the day (peq14 mounted on M9 pistol for a example) ,but mainly they do using only IR lasers (peq2 , peq15 , peq16) on their assault rifles/mgs

In that case upvoted. Handguns with Crimson Trace would be cool to see for civilian weapons.

I'm going to upvote , this is something that it should be in game , IT IS realistic has you showed in the video.