<Trooper> aims for parts of the opponent's body which have already been injured.
"It's nothing personal, but once I start a job I need to finish it."
The default bonus to hitting favourite targets with non-rifles is not determined, so it's impossible to tell if this skill is useful to any other weapon class at all. However, this skill doesn't benefit to Launcher users for sure.
Theoretically, the skill may benefit from Anatomy and Rifles in regard of target preferences. However it is not clear if the default preference is overwritten or not, and how they work with each other. Furthermore, based on this uncertainty, it is hard to tell if the mentioned boosts have any effect at all.
Technically, the skill's effects can be effectively nullified by Hard Boiled, as the latter makes injuries pointless altogether.
To read more about trooper injuries see the Body Parts damage analysis page.