Developer Sultim Tsyrendashiev created a mod for the original Half-Life. It allows transforming Valve's game through the use of the sensational technology.
Half-Life 1 Ray Traced adds ray tracing to the game: real-time lighting, full reflections, and soft shadows.
Ray tracing is relevant not only for the environment; weapons in Half-Life also got an upgrade — the crossbow will shine.
Half-Life 1 Ray Traced is distributed for free via GitHub and can be found here. To use it, you will need the original Half-Life, which can be purchased on Steam.