Bump into 3 people while rolling on the ground before getting up

Wear the outfit of a dead player.

Get hand picked for Shepherd's elite squad.

Kill at least 3 enemies with a single shot from a grenade launcher.

Find 5 trading cards

Learn a player upgrade

Defeat the 1st Colossus

Open a portable safe.

Combine two items together.

Use the Sword to Focus on a Vital Point

Make it to the police station.

Set foot on AR-Y 26 for the first time. I guess that counts as an achievement?