The Targeting Laser was a feature found in TS where a unit would produce a very thin red line to its target just prior to it firing its weapon. It was only used on the Titan and apart form that is unused. The original effect TargetLaser appears to only work with VehicleTypes but there are other ways to create a similar effect.
Target Laser Tutorials
Here you will find a selection of tutorials relating creating a targeting laser effect.
Improved Targeting Lasers (by Tratos)
This will show you how to make very effective target lasers for your units.
This tutorial is very very easy but has good results. Firstly you need to find the unit you want to give a target laser too. For the purpose of this tutorial i will be reffering to the [GGI].
Secondly, ensure that your chosen unit does not have the tag
and if it does ensure that the value is no. This tag gives a 'laser' that is essentially just a red line drawn between the unit and its target and looks rubbish.
Next, choose the weapon you want to apply the target laser to, in the case of the GGI i chose the [MissileLauncher] weapon to give the GGI laser guided missiles. Find the chosen weapon in rules.ini and add the following code to the end of its stats:
LaserInnerColor=*,*,* LaserDuration=** IsLaser=true
Change the *'s to the values you desire. For the colours these will be in RGB (Red, Green, Blue) format (a good red colour is 255,10,10). For the laser duration the value determines the time the laser effect is visible for, a good value is 15-20.
This will draw a laser between the unit and the target when the weapon is fired. The good thing is that the normal projectile (in this case the missile) is also still drawn and the damage only happens when that projectile hits. This gives the effect of a small laser aiming at the target before the missile is fired giving the impression of laser guided missiles. This works best for weapons with a viewable projectile. For weapons with invisible projectiles (or projectiles with a speed of 100) it will just look like the unit is firing a laser.
You can also add the tags:
LaserOuterColor =*,*,* LaserOuterSpread=*,*,*
And these will add a slight glow to the laser, personally i prefer it without these tags but you may not. The values are done in the same way as the InnerColor (RGB format).This effect is great for elite weapons to add a visual identifier that the unit is Elite apart from the chevrons and to mark the weapon apart from regular versions.