The hatchet is a one-handed camp axe that kills any enemy except a bloater in one hit. It is the last bladed weapon you find, first turning up just after you leave Ish's abandoned settlement in the Pittsburgh sewers during The Suburbs.
Eight guaranteed kills from one modified hatchet make it the most efficient melee weapon in the game. Swing it when a fight goes loud and a shiv is no longer an option.
Bloater armor absorbs bladed hits, so it takes several swings at close range where its grab kills you. Burn a bloater first or avoid melee with it entirely.
A fully modified pipe survives more hits, but only three of its swings are guaranteed kills. Every one of a modified hatchet's eight swings is.
Machete
The machete kills in one hit and swings faster than the hatchet, but breaks after three uses. The first one is in Ish's settlement in the Pittsburgh sewers during The Suburbs.
Military sniper
The military sniper is a tripod-mounted bolt-action rifle you only use once, in The Suburbs. A hunter uses it to pin Joel, Ellie, Henry and Sam down in the street; once Joel reaches the house and kills him, you man the rifle to cover the others.
Shorty
The Shorty is a one-handed sawed-off shotgun that sits in your pistol slot. You find it in the Pittsburgh sewers during The Suburbs, on a bench to the left just after you set off the first sound trap.
2x4
The 2x4 is a plank of lumber and the most common melee weapon in the game, especially in Boston and Pittsburgh. It reaches farther than your fists, stuns a human with one hit and lasts four swings before it breaks.