We've all had them, here are a few samples of possibilities.

A lawyer-preacher leading a prayer before the service, made routine opening remarks. As he started on a special plea, he began, "Your Honor," instead of "Dear God."

I was trying to make a point that lack of communication is the major cause of divorce, but somehow things got mixed up and I said ‘marriage’ was the main cause of divorce.

Preaching from:

Matthew 5: "A hill set on a city cannot be hid."

Matthew 12: "as Jonah was in the welly of the bell."

Matthew 2: "they offered unto him gifts, gold, and Frankenstien."

During a Confirmation service, referring to the new converts, the pastor asked the 5 new "convicts" to come to the front of the church. He never knew what he said, but several people had to leave the building because they were laughing so hard.

As I awoke during a sermon the pastor said, "Where the scriptures speak, we speak. Where the scriptures are silent, we sleep."

While studying the intricate dress of the priests in the Old Testament, the preacher came to the part that describes how the priests put bells on the bottom of their robes. He asked, "Why do you suppose the priests had to tinkle." After a second of silence, the class broke up with laughter.