MultiWeapon system/Targeting System

Ive been working on many different things and well, ive also looked in many places but havent found any decent results. My problem is, Im trying to create a weapon that has a targeting system installed into it. Now building the weapon itself is no problem, and I can get projectiles to work well enough, but I want to have a type of effect (or something similar), target somebody (i.e. having particle rays shoot out from an emitter and target a person I select through a dialog menu). Im not sure how to get all that done.

Second, Im also trying to create a variable ammo system for the weapon I spoke of before, somewhat similar to maybe the Samus' arm cannon. I can make huds and the like, but I still dont know how to make the weapon so that when I give a command it fires a certain type of ammo rather than fire all of them or none at all. Any help would be greatly appreciated.

First effect can be done using the particle system, you can "aim" the particles at a key i.e. a person or an object.

As Resolver said the targeting of particles is straight forward, you supply the key of the target as part of the call. look at the llParticleSystem call in the wikki.

Or if your really stuck try this one

Obtaining the key will be via a sensor which you will then use to populate the dialog to allow selection. Be aware that there is a 16 item limit to a sensor return so if you're in a crowded arena you may never detect certain people! Check out llSensorRepeat

A dialog can display up to 12 buttons, so if you want to display 16 you will need to make a paged display. The wikki covers llDialog here

Again if you dont want to do it yourself you could try this thread

Your weapon code will currently have a fixed ammo type, probably in the bullet rez function, just replace this with a variable that you can set via a dialog or chat.