The shiv is a crafted blade made from one binding and one blade. It is your silent kill for clickers, the only way to open shiv doors, and with Shiv Master your escape when a clicker grabs you.
Shiving is faster than strangling, and it is the only way to kill a clicker silently, since clickers can't be choked. It does nothing to a bloater. Don't waste shivs on runners, which you can strangle.
With Shiv Master, Joel can stab a clicker that grabs him from the front, though not one that grabs from behind. On Easy, Shiv Master is unlocked for free.
9mm pistol
The 9mm pistol is Joel's first gun in The Last of Us Part I, picked up from his and Tess's hideout in The Quarantine Zone before they go after Robert. It fires fast, has the most ammo around and stays useful all game as a cheap backup to your heavier guns.
Brick
Bricks are throwables you pick up from the ground to distract or stun enemies. Throw one to the side to pull a patrol away, or straight at someone to stagger them for a follow-up hit.