The Gibson Achievement
Single Player: Complete 20 hacking challenges
This will come very easily while progressing through the campaign, and most players should have it by the time they finish Mission 3. To hack, pull up your visor , and then press on an object that has potential to be hacked. Complete the little mini-game to hack it. You can hack such things as sensors, mines and turrets. Do this 20 times to unlock the achievement.