Use bricks or bottles to lure an infected into attacking a human

Win the water gun fight

Engage in all optional conversations

Win the brick throwing contest

Collect all comics

Break into every locked door using shivs

Find all training manuals

Upgrade and then break one of every melee weapon

Leave Ellie hanging after a job well done

Fully upgrade a weapon

While in stealth, turn off the spotlight generator in Pittsburgh

Find a comic