Raccoon City Chainsaw Zombie

Chapter: 9 · East Raccoon City
Where: The Gas Station (one in the Shop and an armoured one that bursts through the wrecked cars on the west side after the Gas Can) and the upper area of Grimstone's Building 4.

Weak point

The face (a shotgun blast makes it drop the chainsaw). The armoured one barely takes headshot damage.

Tougher Raccoon City zombies armed with chainsaws. A single chainsaw hit can kill Leon (he's cut in half). A downed one can still slide towards you with the blade spinning, and a loose chainsaw still spinning on the floor also cuts: wait for it to stop.

There are three: the first gives you its Chainsaw and the second a Tracking Module (Rare).

Reward

The first one's Chainsaw and a Tracking Module (Rare) worth 5,100 credits from the second.

No published HP. Evil Resource lists a single Gas Station entry; the walkthroughs (IGN, PowerPyx) count two (the Shop one isn't on Evil Resource's list). The game's first chainsaw enemy is a Zombie Doctor in chapter 2.

Step by step

The Gas Station Shop one: backpedal while firing, parry (L) the swing (it damages the Hatchet: sharpen afterwards with L + Y) and give it a shotgun blast to the face: it drops the chainsaw. Pick it up.
The armoured one (spiked helmet; headshots barely hurt it): with the Chainsaw, swing into its swing to clash the chainsaws, land a few hits and step behind it. Without a chainsaw: explosives or the Requiem.
The Building 4 one: blow the upper canister as it walks by and keep the floor holes between you. Requiem or Stacked Hand Grenade. Never let it reach melee range.
The Chainsaw kills most zombies in one swing, but it's slow and can get stuck in a body.