Complete Act 1

Kill all enemies in the beach houses without causing an alarm ("Leave No Man Behind")

Kill three or more enemies by shooting a grenade

Kill 20 enemies from a distance of 600m or greater

Complete any single player mission without using med kits, but taking damage

Buy an upgrade

Assassinate Travis

Assassinate Layla

Approach the church

Eliminate the Saints

Exit the mines

Acquire the Silverballers