The Last of Us Part I

The first Firefly pendant can be found very early in the game in The Quarantine Zone. Shortly after you find a ladder and climb up said ladder with Tess, you'll be in a room with a pool table in the middle. You'll follow Tess into the next room and she'll make a left while you'll continue forward into a bedroom with mattresses on the floor. The pendant can be found on the left side of the mattress near the nightstand. It should be for David Michael Vigil.

If you miss this one, don't fret. There are 30 total in the game. You'll come across one eventually.