For the most part, The Last of Us is meticulously balanced to keep resources scarce and build tension. Some of that tension goes away when you find the flamethrower, which toasts zombies with relative ease. Why include such a powerful weapon? Apparently, Naughty Dog ran out of time.
"That [flamethrower] was something that went in late," creative director Neil Druckmann told VentureBeat. "It felt right in regards to improvisational weapons in the world, having someone craft a weapon like that and Joel finding it. That felt okay. When we were trying to tune it against the enemies, for the longest time it was underpowered against the enemies, through several playtests. We were running out of time, so at that point we just said, 'All right, let’s make it powerful.' That's what we ended up with."
Druckmann doesn't seem to regret the decision, though, since the reaction has been partly positive. "When you get that weapon, you've been struggling for a long time, and all of a sudden you have this flamethrower. There's a sense of relief for a lot players," he said. "'Finally, I’ve got something I can use.' But we've heard different kinds of feedback about the flamethrower."