I just gave a presentation on my doctorate thesis to a group of professors. I invite their comments and criticism by saying "OK, have at me!"

The expression "Have at me" can be used in many contexts. It could mean that others should ask challenging questions, as Judy Anderson shows. It can also invite another person to a fist fight, inviting the other person to take the first swing. . It shows a willingness to accept all challenges. For example: "If anyone disagrees with my answer, then have at me!" .