I usually use the plasma pistol as a sidearm on my 'heavy weapons guy', that is the guy I give my rocket launcher to, even pretty late in the game. Well, it alternates between that and the laser pistol, but I find I kind of like the extra hitting power. Ammunition tends to not be much of an issue. Its cheap to produce and I usually have enough clips in reserve for a while. I often like to use a range of weapons though.. I seem to getinto a habit of having the same squad game in game out. I usually have a sniper who usually uses a Heavy laser or plasma rifle too.