1. Miscellaneous
1.1. Untouchable – Escape a Reaper in the galaxy map
1.2. Eye of the Hurricane – Kill a brute while it’s charging you
1.3. Giant Killer – Defeat a harvester
1.4. Hijacker – Hijack an Atlas mech

Untouchable
Escape a Reaper in the galaxy map.
This can be done at any time when you are on the Normandy and have access to the galaxy map. You will find the galaxy map on deck 2 – combat information center. Enter one of the reaper galaxy systems (the ones with the red symbol) and keep using your scanning pulse. Watch the reaper alertness bar in the bottom left corner. When the bar is maxed out you will see enemy reapers coming in. Fly back to the Mass Relay and exit the area.

Eye of the Hurricane
Kill a brute while it’s charging you.
You will encounter your first Brute enemy relatively early in the game, during the ‘Rescue Turrian Primarch’ mission (Galaxy: Apien Crest, System: Trebia, Planet: Menae).
Weaken the Brute until its armor (basically its health) has only one bar left. Then wait until the Brute is trying to tackle you and kill it while it is running towards you. Make sure your team is not killing the Brute by accident. Reload the last autosave if they do. Moreover, you should save your game manually before the fight starts. Just in case something is going wrong. There will be other chances to get this later on, so don’t worry if you missed it here.

Note: This was played on normal combat difficulty. You can change your difficulty settings at any time in the options menu.

Giant Killer
Defeat a harvester
One of the first chances to encounter a harvester is during the ‘Extract Turian Survivors’ mission (Galaxy: Krogan DMZ, System: Aralakh, Planet: Tuchanka).
It’s recommended to set the difficulty down to narrative. You will run into multiple harvesters during this mission, but they fly away when they are close to death. On high difficulties you might not have enough fire power to kill them fast enough.

Hijacker
Hijack an Atlas mech.
Important: This cannot be done against the first Atlas Mech you encounter on Sur’ Kesh! It works on all other Atlas Mechs, but not the first one!
The video shows a location during the ‘Locate Bomb’ mission (Galaxy: Krogan DMZ, System: Aralakh, Planet: Tuchanka). There will be other opportunities during the course of the story, so don’t worry if you miss this one. Choose a weapon of your choice and shoot the glass of the Mech. The glass will shatter once the armor is halfway gone. Quickly take out the driver with some precise shots, run in front of the mech and press X (PS3) / A (Xbox 360) to enter it.
Note: This was played on Normal Combat Difficulty. The weapons do not matter, as long as they fire shots and not explosives.