If by "gravity neutral" you mean "not affected by gravity" the answer is none. Gravity is an attribute of curved space-time and thus everything in space-time is affected. Even massless photons curve in the presence of massive bodies.
Subatomic particles do have gravity. However, their gravity is very small.
Sediments are mainly caused by gravity acting upon eroded particles, and of the bodies of dead plants and animals.
No one really knows if ghosts actually exist. But if they do they are formed by particles. Particles are attracted by gravity.
Yes, particles in the nebula attracted to one another by gravity?
Gravity IS a source of natural forces.
gravity
The process of removing rock particles by wind, water or ice is called erosion. This can also be the removal of enamel from teeth by acid (acid erosion). To be more precise, this is weathering process of the rock where in the rock is broken into small particles by natural forces like wind, water, ice or gravity to get it eroded.
All particles with mass are attracted to one another by the force of gravity.
Gravity
Very generally, gravity is the by-product of a frequency vibration between two or more atomic particles creating a subatomic vacuum between the two or more particles.
The gravity traps everythings on a planet.
This is erosion.