Driver instruments and related methods are disclosed herein, e.g., for applying a fastener to a bone anchor. Various features are disclosed for retaining the fastener to the driver instrument, such as tapered drive tips, as are various features for impacting the driver instrument into the fastener, such as slidable slap-hammer type handles. Driver instruments with interchangeable handles or handle geometries that can be changed without separating the instrument from an attached fastener are also disclosed.