Live To Tell by Madonna, that's a good example of what RISKY TRULY ITS! she had just finished her Virgin Tour and GP and Media were not ready to see that Madonna, alone, in a black and empty set, singing a power ballad, as a first single, and it worked, especially counting that she were serving more 80's and sexed tunes in her previous work, with a different singing method, she slayed!
IIWAB was after B'Day, but Single Ladies kept urban cute, and then it crossed over. In fact SL made me buy ASF not IIWAB. It worked for pop, and AC lovers. Like Halo did in the UK here (they think it's one of her best singles, over the r&b uptempos).
If I Were A Boy comes to mind.
It's a sound that wasn't too commonly associated with B.
Run The World is, in fact, ahead of it's time with the weird song structure, sample or not.
It and those mentioning "Run This World" did not work, though. Therefore are ineligible for this discussion.
I echo Jennifer. "SexyBack" was a hit or miss situation and did wonderful. I don't feel like thinking too far back, seems this thread will end soon enough.