Tesla
Without his work,we would not have electricity for almost every household,the electric motor would not exist causing alot of modern hardware not to be able to exist in small version(computers would have to be cooled with a combustion engine propelled fan,imagine one of those puppies in your laptop.Not much of a laptop anymore).Not to mention his work on radar and radio communicator technology which he made advance by at least a decade.
His wireless electricity technology is still almost magic by today's standard(only recreated by the MIT with the distance only a fraction of the distance Telsa achieved).As if all that isn't enough,he brought to the world the first radiocontrolled robots.That's right drones have existed for a century now.
Too bad he was absolutly batshit crazy and half of his work wasn't written down and lost.Man,if he was alive today,he would look in the sky,notice the dissapointing lack of flying cars and build one on the spot,then procede making a world wide electricity network powered by a giant fusion reactor.