The often-quoted "money is the root of all evil", while technically a valid quote, leaves out a crucial section that changes the meaning. It actually says that the love of money is the root of all evil, or a root of many evils depending on which translation you use.
Another common misquote concerns the Garden of Eden's "Tree of Knowledge of Good and Evil," often mislabeled as just the "Tree of Knowledge." Considering the original Heberew, it should really be translated as "Tree of Omniscence."
"When in Rome, do as the Romans do." Paul said something vaguely similar, but not quite...
"I am all things to all men, that I might win some of them" means going the extra mile. Roman soldiers were entitled to make conquered Jews carry their packs, but only for a mile.
"Pride goeth before the fall". Parodied hilariously in Bill Fitzhugh's "Pest Control", as two Columbian drug lords debate semantics and paraphrasing right after they shot a trespasser to death and had his body torn apart by dogs.
"Spare the rod and spoil the child" is usually considered a easier-to-remember summation of Proverbs 13:24, "He who spares the rod hates his son, but he who loves him is careful to discipline him."
Mary is not the Queen of Heaven. "The queen of heaven" described in the Bible is an entity that should be ignored if you come away with the most positive possible reading of her, is possibly an enemy of the Jews Mary descended from, and predates Mary by seven hundred years.
It's popularly assumed that the Roman soldier who pierced Jesus' side to confirm his death had his blindness cured when he touched his eyes with his blood-stained hands. This actually isn't anywhere in the Bible, but comes from a medieval best-seller The Golden Legend. And who would hire a blind soldier anyway?
The bit about Mary Magdalene being a harlot. She was actually a former victim of demon possession, while the harlot was from another passage. Also the bit about her being in love with Jesus, which might qualify as one of the oldest examples of Shipping by the fandom.
Many other notions that have become canon in modern Biblical religions (both Christianity and Judaism) actually never appeared in the Bible, or require an extremely strained reading of Scripture to arrive at. Purgatory appears to be a Catholic invention, the pre-tribulation Rapture was invented (or at least popularized) by John Darby in the 19th century, etc..
The popular phrase "God helps those who help themselves" is not found in the Bible. Nor was it said by Benjamin Franklin, the most common other source. Variants are found in the writings of Ancient Greek thinkers and it was first encountered in its modern phrasing in the work of Algernon Sidney, a British soldier, politician, and anti-Monarchist political theorist.
Name's the Same: The Catholic and Orthodox Bibles have four different Judases. One is a heroic freedom fighter, the other is an apostle and another appostle betrays Jesus. There was another Judas who lives in Damascus.
The Antichrist/'false messiah' concept. Revelation describes a despot ruler and his false prophet, but there's nothing about him actually claiming to be any kind of Jewish messiah.
Judas' motives (e.g. claiming he was a Miser Advisor) for telling Jesus that they could have sold the oil and used the funds for the benefit of the poor.
The fruit of the Tree of Knowledge being an apple.
Word of Saint Paul: Orthodox and Catholic Christians use historical extra-biblical tradition and history gathered over centuries, as well as bishops to teach and define Biblical texts to form their faith teachings. Protestant Christianity generally takes the Bible alone as the sole source of divine information. A few, such as the Mormons, Take a Third Option with tomes of their own to supplement.