I’d go with Darwin, because his ideas really changed the way people thought about life, and brought the whole field of biology into a logical framework. Without him, biology would just be a collection of facts about different animals.
Leonardo da Vinci, even if he wasn’t simply a scientist, but a proper genius! Nowadays you only find people that are really good at one thing (me included!), but he was (and I have only just found this word) a pantheist, that means he did everything. He was a painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer!
Oooo – that’s a tough one, there are so many great scientists. I can’t decide who my favourite is but I like Brian Cox, because he’s lovely and friendly on the telly and does a great job of explaining physics to people like me that aren’t very good at physics. If you asked me again in 10 minutes I’d probably give you a different answer though 🙂
Charles Darwin – for bringing about the realisation that we are not apart from nature – but a product of it. Such an important discovery, and it’s consequences are so profound that there are still some people who cannot accept it. That’s a pretty amazing CV for a scientist!
There have been lots of amazing scientists, but I think that Charles Darwin is the one I respect the most. His theory of evolution is completely central to most of biology, it changed the way scientists think completely. And it was very controversial, so he was pretty brave to publish it.