protons
The proton is one of the three basic particles that make up the baryonic atom. It is a baryon (heavy particle), a hadron, a strongly-interacting fermion, and one of two nucleons (the other is the neutron). It is composed of two up and one down quark, for a total charge of +1. Its antiparticle is the antiproton.
Cosmic strings were no wider than a proton but had gravitational fields as powerful as a black hole. (TNG: "The Loss")
The crew of USS Voyager found themselves being bombarded by protons after Q reduced them and their ship to subatomic proportions in an attempt to escape from Q. Captain Janeway suggested releasing a positive ion charge to repel the protons, but the crew and ship were transported from the location before the attempt was made. (VOY: "Death Wish")