Here's what I think would make a great banner to hang out in front of a church. Granted, it's too long, but it beats most of the trite sayings or verses that one usually sees... maybe just the first sentence?
Therefore my faithful request and admonition is that you join our company and associate with us, who are real, great, and hard-boiled sinners. You must by no means make Christ to seem paltry and trifling to us, as though He could be our Helper only when we want to be rid from imaginary, nominal, and childish sins. No, no! That would not be good for us. He must rather be a Savior and Redeemer from real, great, grievous, and damnable transgressions and iniquities, yea, from the very greatest and most shocking sins; to be brief, from all sins added together in a grand total.
-from Martin Luther's letter to Spalatin.