To aim (a gun) - which word is the correct one for "aim"?

Google translate offers many alternatives, but no indication to which one is used for gun...

verb
стремиться seek, aim, aspire, work, gravitate, long
целить aim
целиться aim, point, peg, level, present
добиваться seek, achieve, strive, obtain, get, aim
нацеливаться aim
прицеливаться aim, take aim, sight, draw a bead on, point, zero in
метить mark, label, aim, drive at, notch, raddle
иметь в виду keep in mind, bear in mind, have in mind, mean, have in view, aim
наставить point, aim
домогаться solicit, covet, aspire, aim, seek after, exact
норовить aim

целить/нацелить пистолет

нацелить пистолет, но прицелиться (it is understandable that you have some sort of weapon) - Он увидел кабана и прицелился. If you need to specify - прицелиться из ружья, из пистолета. Целиться also possible in these cases, imperfective. If you need to specify te aim - (при)целиться в кабана.
Наставить пистолет - also possible but the meaning that you just raise the gun to frighten somebody standing close to you without aiming as a process. Он наставил на меня пистолет и потребовал мой кошелек.

навести пистолет also fits. "наставил" is a close range situation.

He aimed the gun at her. - Он навел на нее пистолет. Or simply Он прицелился в нее.

but 'gun' doesn't always translate as "пистолет". it can be any weapon, while technically пистолет is a handgun.

Thanks for the help, guys. :) I wish there was just one word :P

That is hardly possible. Every language uses different ways to convey the same idea. There are many words which can be related to it from different points of view. It would be better if you learned the internal logic of how the words are used.

нацеливать/нацелить (transitive verb) is derived from "цель" (aim, purpose, goal). So, it directly corresponds to the English "to aim (a gun)": нацелить пистолет на кого-либо (Accusative).
прицеливаться/прицелиться (intransitive verb) conveys the same idea without specifying an object: прицелиться в кого-либо (Accusative).

Compare: он нацелил ружьё на зайца = он прицелился в зайца (ружьё = a rifle; заяц = a hare). The first one can be translated as "he aimed a rifle to a hare", the second one is just "he aimed to a hare".

направлять/направить (transitive verb) is "to direct something to": он направил ружьё на зайца = Lit. He directed a rifle to a hare.
This verb is related to the noun "направление" (direction).

наводить/навести (transitive verb) is something like "to lead something to": он навёл ружьё на зайца = Lit. He led a rifle (to point) to a hare.
"водить/вести" is "to lead someone or something", "на-" is a prefix of direction.

наставлять/наставить (transitive verb) is something like "to put something on": он наставил ружьё на зайца = Lit. He put a rifle on a hare.
"ставить" is "to put, to place" with the same directional prefix "на-".

приставлять/приставить (transitive verb) к + Dative: он приставил ружьё к голове зайца = Lit. He put a rifle against the head of a hare.
- this one can be used when you touch the hare's head with the tip of the rifle.


In English, there are also different ways to express it: to aim, to direct, to point, to target, ...