Perhaps, one of the most common arguments against christianity is the assertion that Jesus never actually existed. I recently stumbled across this video of Bart Ehrman that I think sums it up pretty well. Keep in mind Ehrman is not a Christian and in fact left Christianity after going to Moody Bible Institute, getting his M.Div and PH.D. from Princeton is now is a professor at UNC and an expert in New Testament Studies.
Check out what he has to say when someone in his audience says that he doesn’t believe there is evidence that Jesus actually exists. Also, keep in mind the award in front of him is from the Freedom From Religion Foundation who gave him the award because they believed he has been exposing religion.