Jesus is naturally the first person to come to mind. Echos from the life he lived 2000 years ago are still reverberating around the world and affecting millions of lives every day.
Following Jesus, the person who has probably had the most impact on our lives today is inventor Nikola Tesla. The induction motor he invented is in almost every appliance you can think of. The AC power supply that gives us electricity came from Tesla. So did the automobile ignition system. He discovered x-rays. He also invented - among other things - radar, flourescent lighting, remote control, and the radio. (Yes, I know: in the history books they told us Marconi invented wireless radio, but he did it using 17 of Tesla's patents, and the U.S. Supreme Court eventually declared Tesla the true inventor of radio.)
Anyway, I have a hub on Tesla if you want to learn more.