Add the ability to rotate the map. Is very useful for mobile devices, for example in a GPS navigation app.
Maybe use hammerjs (if available) to allow the rotation of the map using two fingers on mobile devices.
OpenLayers3 supports this out of the box.
Julian Perelli commented
Link to openlayers3 example http://ol3js.org/en/master/examples/full-screen-drag-rotate-and-zoom.html