Blister Head

Type: Mutations
Chapters: Chapter 3: Isolation Ward Lobby (2, after you take Emily to the Security Manager's Office) and any zombie you left with its head on. Chapter 4: 3F, Lounge (1), Meeting Room (2) and the secret-lever wave. Chapter 5: Furnace (1). Chapter 6: Collection & Testing East (6) and Exit Passage (1). Chapter 7: the Chapel (from the Blister Borne's cysts). Chapter 9: Building 4, Maintenance Platform and Grimstone Building Rooftop (1 inside the hanging crate).

Weak point

The head and tumour: the kill has to destroy the head or the whole body.

Tactic

A double mutation: the corpse of a zombie whose head you didn't destroy stands up later (usually when you pass by again), with a tumour over its head, more strength and agility, and a lethal grab. Prevent it with a headshot kill that destroys the head, a Hemolytic Injector, a Hatchet finisher or a stealth kill.

Grace: a Requiem round before it charges, or stun it and inject it. Otherwise take another route.
Leon: about 3 shotgun blasts put one down, then the Hatchet finisher to the head (counts for Chop Chop). Parry (L) its punches and grabs, then pistol, kick and hatchet. Kicking it into a wall sets up the finisher. A thrown axe also staggers it.
Chapter 9, Grimstone Rooftop: shoot the hanging crate down.

Drops

Nothing fixed.

Standard (Classic) and Insanity: 2 more on Raccoon City's Main Street after the Gas Can with Fuel (chapter 9; not on Modern). Insanity: they appear from Leon's very first street (2 in Wrenwood) and on the West Overlook (chapter 7), and zombies can mutate on the spot. One Steam player counted about 30 hatchet hits and a full pistol magazine for one on Insanity: use a shotgun or rifle knockdown there and finish with the hatchet. Save shells for the 3F room at the end of chapter 4.