Photons are mass-less particles as are gluons. There are four fundamental forces, electromagnetism, gravity, the weak nuclear force which cause quarks to change from one flavor to another allowing for certain nuclear processes to occur, and the strong nuclear force which holds the nucleus of atoms together despite the significant tendency of protons to repel against on another. Each of these forces has one or more "transmitter" or "carrier" particles, photons for the EM, gravitons for gravity, gluons for the strong force (since they "glue" protons and neutrons together) and the vector bosons (W+, W-, and Z) for the weak force.

Forces such as friction are actually a result of one or more of these fundamental forces (in the case of friction its actually a result of the electromagnetic force which causes particles of opposite charges to attract one another causing the particles at the edges of the surface and mass to intermingle and resist movement).

Finally space isn't technically a vacuum, there's actually a very small density of mass throughout the galaxy, but much of it is actually filled with photos and neutrinos and possibly dark matter and energy particles as well, though these are only presumed to exist because of certain observations regarding the expansion of the Universe. As far as I know the Standard Model doesn't account for these particles.

But to answer the initial question Gravitons, almost certainly exist in one form or another. They almost certainly have no mass and since gravity is itself a very, very weak force when compared to the other forces it's unsurprising that it remains the last force particle undiscovered. Yet because it is mass-less this allows gravity to occur at the speed of light (since there is no mass it is able to devote its entire space-time velocity to spatial movement). Which leads to an interesting thought if the Sun were to suddenly disappear completely it would take around eight minutes for anyone on Earth to notice the change, whether it be because of the complete lack of sunshine, or the radical change in the motion of the planet.

I discovered the Graviton Particle. You could ask me...alfredschrader@aol.com - NPA Scientist

You're describing some sort of electromagnetic attraction, gravity is a separate force. Gravity is the force produced by the distortion of spacetime due to matter. Imagine spacetime as a flat piece of flexible plastic. When a ball is dropped onto the surface the ball creates a depression. If a marble were to be rolled onto the plastic from one of the edges and passed close enough to the depression it would orbit around the depression. If the marble's momentum was great enough it would immediately escape this orbit, if it was too low it would plummet towards the larger ball. The gravitational force exerted by say the Sun on the Earth is very similar (though in three dimensions rather than two). Likewise the Earth exerts a force on the Sun and the Moon, and perhaps most importantly on everything on its surface.