Lucretius:
"Too often in time past, religion has brought forth criminal and shameful actions. ...How many evils has religion caused!"
"The nature of the universe has by no means been made through divine power, seeing how great are the faults that mar it."
"All religions are equally sublime to the ignorant, useful to the politician, and ridiculous to the philosopher."
"Fear was the first thing on earth to make gods."
"Not they who reject gods are profane, but those who accept them."
"We, peopling the void air, make gods to whom we impute the ills we ought to bear."
"There is no murky pit of hell awaiting anyone. ...Mind cannot arise alone without body, or apart from sinews and blood. ...You must admit, therefore, that when the body has perished, there is an end also of the spirit diffused through it. It is surely crazy to couple a mortal object with an eternal and suppose that they can work in harmony and mutually interact."
Others:
"It is expedient that gods should exist; since it is expedient, let us believe that they do." (Ovid)
"From the moment of death onward, the body and soul feel as little as they did before birth." (Pliny the Elder)
"The superstitious man wishes he did not believe in gods, as the atheist does not, but fears to disbelieve in them." (Plutarch)
"Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful." (Seneca)
"It is for the good of states that men should be deluded by religion." (Statius)
Please feel free to contribute with further examples or with thoughts and opinions.