Nelson Mandela
Dalai Lama
A lot of the ones previously listed.
I agree that most of the people I'd put on the list are not famous. Like we work with a guy at the zoo who lives locally at the end of our irrigation ditch system. His dogs always came home smelly from playing in the water so he wanted to find a way to clean it. He invented islands that float in the water that have plants/grass whatever growing on them and they purify the water. We use them at the zoo that I volunteer at for some of our exhibits and ponds and they're starting to be used internationally. Islands that grow plants that purify water, astounding worldwide water quality applications. He's already getting massive orders.
Another one is Jay Kirkpatrick. He runs the science and conservation center at our zoo. He has developed a contraceptive that can be used for wild animal populations by just darting the animals. It's natural, no side effects, the animal can live and have normal behaviors. Zoos all over the world use it plus a lot of urban populations to control things like deer in urban parks. They work with a preserve in South Africa to control the elephant populations.