The Molotov Cocktail is a weapon featured in Resident Evil Zero.
After getting an A rank in Leech Hunter (which unlocks infinite ammo for all weapons), a specific Molotov Cocktail can then be found in Room 201 of the Train in the main game that can be used indefinitely. Molotov Cocktails actually created even after getting the A rank will still have limited use.
Molotovs are fairly common. While effective against most enemies, they are singularly effective against a Mimicy Marcus, often destroying the mass of leeches after three attacks. However, they can be rather problematic to aim, and there is a short wind up animation before the cocktail is thrown. The splash will cause enemies within a short range to burst into flame, meaning there is a reasonable margin for error.