Memory Safety Without Runtime Checks or Garbage Collection. They sorta cheat, but you sorta have to.
Adaptive Functional Programming. Basically, a relatively non-invasive transformation on an algorithm (sorta reminds me of CPS) lets you tweak its inputs and have it automatically only update the parts that changed. I think their example was taking quicksort, adding one number to the input, and having it resort in log n. Long, but the second half goes into proofs and my eyes glaze over.
And, um, drawing a blank.
