Conventional gravity obeys the inverse square law, but you don't necessarily need to have that all the time.
I'd like custom curves for a star or planet's gravity, as a simple example, instead of gravity getting weaker the farther out you go, it becomes stronger.
For that example, you could make "Gravitational walls" that would be impossible to overcome with conventional thrust alone, and requires you to maximize your speed with multiple gravity assists.
Another example is gravity staying relatively constant for a very long range, then suddenly falls of slowly like normal. This can help simulate things like dark matter in a galaxy, and could be useful for creating binary systems where the center isn’t necessarily the entire source of the gravity.