This answer does have similarities to Kromey's proposal for artificial gravity by positive and negative gravitons. Congratulations, Kromey, for thinking of something good. However, our mechanisms are different.
Assume there is a field that can be generated between two plates. This field has the property of causing the curvature of local space to increase proportional to the amount of energy pumped into it. The increased curvature of space create what is effectively an artificial gravity field and with the preferred direction being downwards to what has been designated as the floor.
This means spacecraft will have internal gravity fields anywhere on the vessel where pairs of gravity plates are installed. The strength of the artificial gravity will be determined by the amount of power stored in the curvature making field. For convenience this field will be called a barygenic field. "Barygenic" has the literal meaning of "heavy-making" which seems appropriate.
If power fails to the barygenic field the strength of artificial gravity will fade away as more energy is drained from it every time someone drops a tea cup or jumps up and down. This assumes the barygenic field has zero effect when turned on, and it is only the energy stored in the field that creates the "action" of gravity.
Gravity guns cannot work with a barygenic field system. Any munition accelerated to a lethal velocity would collide with the opposite barygenic field plate.
However, a form of gravity drive is possible. This would consist of an extremely powerful barygenic field system built around a major structural member of the spacecraft. This structural component is subject to high acceleration which will require pumping extremely large amounts of power into the barygenic field.
The maximum amount of acceleration this type of gravity drive can generate will limited by two factors. One, by the amount of power a spacecraft can generate safely. Two, by the amount of acceleration passengers and crew can endure safely and in comfort.
If barygenic field gravity drives, here this stretches the already rubbery limits of speculative physics possibly beyond any reasonable bounds, can embrace the entire fabric of a spacecraft and provide acceleration for its motion, there might be one interesting side-effect.
Spacecraft as shown in movies and TV, with artificial gravity, always configure their artificial gravity systems such that the floors are at right angles to the axis of acceleration and motion of the vessel as if spaceships were marine vessels or aircraft. So the nose of a spaceship is located in the front instead of overhead which is the realistic configuration for a vessel under continuous acceleration.
Possibly this can be explained if the barygenic fields producing artificial gravity inside the spacecraft interfered with the main barygenic field responsible the spacecraft's gravity drive. Then the front of the vessel will be in its direction of motion.
No real physics was harmed in the making of this answer.