Each puzzle has had a number removed from its center square. There is a unique number that can be placed in that square such that the puzzle then has a unique solution. (There are other clues for that square that yield solutions, but those solutions will not be unique given the clue.)Nurikabe
In order, the removed clues are 6, 1, 3, 1, 4, and 5. Converting into letters gives the answer, FACADE.