According to our current understanding of particle physics, there are a few examples of subatomic particles that are believed to have zero rest mass. Rest mass refers to the mass of a particle when it is at rest.
Photon: The photon is the particle of light and other forms of electromagnetic radiation. It is an elementary particle that travels at the speed of light in vacuum and is massless.
Gluon: Gluons are the elementary particles that mediate the strong nuclear force, which holds quarks together inside protons, neutrons, and other particles. Gluons are believed to be massless.
Graviton (hypothetical): While the existence of the graviton has not been confirmed, it is a hypothetical particle proposed to mediate the force of gravity at the quantum level. In certain quantum gravity theories, the graviton is considered to be massless.
It's important to note that these particles are considered to have zero rest mass based on our current theoretical understanding. However, experiments and further research are ongoing to confirm the properties of these particles and explore the nature of mass in the context of fundamental particles.