Hand to: Cersei Lannister
In case you were freaking out too much over what was happening to notice, when Cersei is crowned queen in the season six finale, you can indeed see Qyburn wearing the unmistakable pin of the Hand. It's not exactly surprising considering how few allies Cersei has left these days, but it can't mean anything good for the future.
Qyburn has been gaining favor with Cersei in little ways since season four, and now that he's in such a powerful position, it's easy to see how dangerous he could be on a grand scale. Anyone who would willingly bring the Mountain back to life isn't exactly someone you'd want whispering into the queen's ear. He has had no qualms about helping Cersei's cause, no matter how unpleasant the methods (ahem, using children to murder?!), and he's always stuck by her, even through her arrest and trial in season five.
After Cersei's insane power grab in season six, who knows what might be in store for King's Landing — but it's safe to say that whatever plans Cersei has, Qyburn will be there to help carry them out.
