Unique gravity

Is there a way to have gravity be unique for certain objects? For example, while most things in the level would move normally, you could have a specific cube that “falls” from left to right?

The easiest way would to be to use ApplyForce within an update method in a script like this:
C#

void Update()
{
    cube.rigidbody.ApplyForce(Vector3.Right * (float)gravityStrength);
}

Of course you want to make sure the object has the rigid body component attached.