Collect all trophies
Complete Left Behind
Use bricks or bottles to lure an infected into attacking a human
Find all notes and artifacts
Win the water gun fight
Defeat Black Fang without getting hit
Played the Jak X game in Left Behind
Engage in all optional conversations
Survive all of Ellie's jokes
Win the brick throwing contest
Complete Part 1
Collect all comics
Find all Firefly pendants
Break into every locked door using shivs
Find all workbenches
Find all training manuals
Find all workbench tools
Upgrade and then break one of every melee weapon
Pet Buckley the dog
Leave Ellie hanging after a job well done
Fully upgrade a weapon
Open All Safes
Ride the sewer contraption with Henry and Sam
While in stealth, turn off the spotlight generator in Pittsburgh.
Craft every item
Find a comic
Pick up Frank's note after it's discarded
Find one training manual
Find a Firefly pendant