There are many economists of the 20th century who are identified with laissez-faire economics since laissez-faire is the idea that is most adhered to by classical economists. Some of the more famous names who have been particular advocates of laissez faire include Ludwig von Mises, Friedrich Hayek, and Milton Friedman.
All of these men are well-known to conservative economists. They all strongly support the idea that the government should stay out of the economy as much as possible. Hayek, in fact, wrote a book entitled The Road to Serfdom in which he warns that any serious moves away from laissez-faire will lead to a move to socialism and ultimately to the destruction of human liberty.
There are many other famous economists we could name as supporters of laissez-faire, but these are three of the most important.