Of the evolutionary biologists, Richard Dawkins is the big one. Jerry Coyne is another. Those are the only two names that spring to mind at the moment, though I don't know any evolutionary biologist who is as large a name as Dawkins. (Daniel Dennett, while not a biologist himself, could count as another who likes to use evolutionary theory to further an intellectual case for atheism.)
In physics, things get wild as well. Laurence Krauss is the most radical anti-theistic polemicist I can think of, but Sean Carroll tends in a similar direction. Then there are figures like Neil deGrasse Tyson and the late Stephen Hawking who are not quite anti-theists but should probably be a bit more cautious about mixing science and anti-religion in the public sphere.
I would definitely consider Dawkins an anti-theist rather than an atheist. His agenda is very obvious, since he's basically built a career out of it.