I'm still waiting for the nanobots that we were promised two decades ago.
Imagine a billion nanobots swarming inside your body, networked [1] and analyzing every cell they come across. Over time, they build a gigantic database of your cells. Then they'll be able to use some heuristics to determine whether any given cell is a menace to your health. If it is, they either tag it for apoptosis or terminate it with a micro laser, depending on how reliable they think each method would be.
Movie material today, reality tomorrow. When this happens, I'll finally welcome the combination of "cure" and "cancer" in the same sentence.