Stephen Hawking
A legendary figure among the contemporary relativists and quantum cosmologists. His ealier works were on the relativistic theory of black holes. However, the gravitational collapse, if the time is reversed, may be quite analogous to the beginning of the whole universe according to the standard bigbang theory. But, of course, quantum mechanical twists come in if we want to talk about the beginning of the tiny universe, smaller than the Planck length 10^-33 cm. Here is the battle field of quantum cosmology and quantum gravity. After a series of important professional contributions in these fields, Hawking published A Brief History of Time (1988). This made him one of the world's most famous celebrities. To mention a few of his dicta, "a black hole is not really black", "a black hole has an entropy", "a black hole may evaporate (especiallly at an early stage of the universe)" , and "no boundary condition for the universe".
See Hawking short-short [in Japanese]