The Federalist has published a fun little article entitled The Eight Biggest Myths about the Bible. They are, in order:
Myth 1: Money is the root of all evil.
Myth 2: Thou Shalt Not Kill
Myth 3: The Bible Makes Wives Subservient
Myth 4: Judge Not Lest Ye Be Judged
Myth 5: The Bible Condones Slavery
Myth 6: The Bible Condones Rape
Myth 7: If You Oppose Gay Marriage Yet Eat Shellfish, You are a Hypocrite
Myth 8: Isn't the God of the Old Testament an Angry Tribal Deity?
I'm not sure that these are the biggest myths, but I do think that these are pretty fundamental myths that people use to try to hammer Christians. The answers given appear to be quite sound. Some are obvious, e.g., the Bible doesn't teach that money is the root of all evil, but rather that the love of money is the root of all evil. Some are a little more subtle, e.g., Judge not lest ye be judged is not a Biblical mandate against judging but against hypocrisy. Some deserve a great deal more detailed argument, e.g., it is very difficult to explain in a couple of paragraphs why God is not some type of blood-thirsty God in the books of the Old Testament. Still, the article does a nice job of highlighting some quick answers. I recommend it as a primer or a refresher.