we recently used bubblesort in an optimality proof for an algorithm. We had to transform an arbitrary optimal solution represented by a sequence of objects into a solution that was found by our algorithm. Because our algorithm was just "Sort by this criteria", we had to prove that we can sort an optimal solution without making it worse. In this case, bubble sort was a very good algorithm to use, because it has the nice invariant of just swapping two elements that are next to each other and are in the wrong order. Using more complicated algorithms there would have melted brains, I think.
Greetings.
