Well I think that when the unstopable force would meet the unmovable object 2 things could happen:
1. The entire universe moves along with the unmovable object which relatively is still in place(therefor not moved) whyle the unstopable force would seem to have stoped in place when it is actually moving the universe.
2. There would be a rift in space-time and the force would go through the object and the object would stay in place (or it wil be the end of existance, but that's thinking pessimistic)