Weapon and Ability Achievements Guide

General information
Almost every ability each of the main three classes (Engineer, Adept, Soldier) has is tied to an Achievement. Weapon achievements require 150 kills to unlock. Ability achievements require 75 uses to unlock. Offensive abilities like Lift and Overload and defensive abilities like Shield Boost and Barrier can be used at any time. You can only unlock weapon and abilty achievements using your main character, not with your party members.

Ability achievements
One easy way to get them is to cast your offensive abilities on the Mako. This can be done with every ability except for AI Hacking, Lift and Singularity. To get the achievement points quickest, get a character to level 10, save on an Uncharted World, and then put all of your points into the skill you want to unlock. The Mastery will significantly decrease the overall time you will have to spend. Cast until you unlock it, then reload and repeat with the other skills.

Weapon Achievements
Your character does not need to have the corresponding skill to unlock weapon achievements. This means you do not have to play a Soldier to attain (for example) the Assault Rifles achievement, you can get it with any class. A good way of doing this is killing tame creatures (like Gas Bags, Space Monkeys and Shifty Looking Cows) with an assault rifle. Once you have access to the Master Spectre Gear, you can fully replace your main weapon with the HMWA. Because of its high precision rating, you will be able to easily kill your enemies without any training, earning you the achievement sooner or later. If you are playing a Bastion, you can also exploit the fact that your team mates will rarely attack enemies held in Stasis - so use it as often as you can to get more kills for yourself.

Bonus Talents
Once you unlock a weapon/ability achievement, you can add said weapon/ability as a Bonus Talent to any character you create after you earned the achievement and upon start of any new game and character. You do not have to finish a playthrough, as you get the bonus immediately upon gaining the achievement. This allows you unlock a weapon for some classes, such as Adept and Engineer. This makes them a lot more dangerous than using the class's standard pistols. The "kill count" for these achievements carries over from character to character. Thus the player could unlock every weapon by replaying Eden Prime with different characters. However, a less tedious approach would involve completing the game with a Soldier, a class proficient with every weapon, to unlock these weapon achievements. It is highly recommended to unlock at least Assault Rifles. However, for less close-combat oriented characters, sniper rifles provide an alternate strategy for avoiding damage. Other talents such as Electronics are useful for Soldiers, Adepts or Vanguards because of the shield bonus it grants (Useful for both survivability and the Tactician Achievement). Other skills such as First Aid or Medicine allow the player to cover up weaknesses in their party. For example, Soldiers could also efficiently learn Medicine in order to improve their first aid and use Neural Shock so that they are better suited for fighting at the front line.

It is helpful to plan multiple playthroughs so you can unlock certain abilities to have on another class. For example, your first playthrough as a Soldier to unlock all of the weapons achievements. The next one as an Adept with Assault Rifles to unlock all the Biotics ability achievements. Then you could play through as an Infiltrator with Singularity, so you could pull people out of cover to snipe them.