I think the big reasons gravity is different are as follows: * very weak (many orders of magnitude less strong than the other forces) * no positive/negative m

I think the big reasons gravity is different are as follows: * very weak (many orders of magnitude less strong than the other forces) * no positive/negative mass 'charges', the gravitational force is attractive only. * works via curvature of spacetime (according to Einstein), instead of the exchange of force particles (e.g. instead of by jiggling fields)