In the final book of Harry Potter (DH) what wand does harry use when he battles voldemort?

voldemort kills snape cos he thinks snape is the master of the elder wand but its actually draco malfoy and as harry disarmed draco at malfoy manor making him master of the elder wand. he uses Draco's wand to fight voldemort and because harry is the master of the elder wand when voldemort tries to kill him his curse backfires. again.