The Bulletproof Vest is an equippable item from Silent Hill 3. The vest is found in the Otherworld version of the Central Square Shopping Center, hanging inside of the alternate clothing store. It reduces the damage taken from monsters by about 15%, but makes Heather Mason run slower when it is equipped. Because of this, it is mandatory to take off the bulletproof vest in order to survive the red mist that pursues Heather at the end of the Borley Haunted Mansion. It also prevents any damage taken from blocked attacks.
It does not physically show when Heather has it on, as Heather wears her own vest over it; the protective vest isn't even conspicuous when all she has on is a tank top.
This item can come in handy while going for the 10 Star Ranking. The 75+ melee kills will become easier to get if used the right way.