There are, I suppose, a variety of possible candidates, but today I submit John 14:6 as the single most blatantly misquoted saying from Jesus' entire ministry. Lifted completely out of context, Jesus' statement is usually presented as "Exhibit A" for Jesus' establishment of the exclusive religion of Christianity as the sole route out of hell...and the reason everyone who doesn't acknowledge the speaker's version of orthodoxy is clearly hellbound.
Someone once said "a text out of context is merely a pretext," and nowhere does this statement apply more forcefully than to John 14:6. The context is a long heart-to-heart that Jesus had with his disciples at the Last Supper (see the beginning of John 13), on the subject of his impending crucifixion. This particular discourse actually begins at John 13:31 and continues unbroken through chapter 17. In it, Jesus is talking about his death and encouraging his disciples to stay strong, faithful, and together through the trials that are coming. His disciples aren't exactly tracking with his message, though...at least not at the beginning of chapter 14. Having just told the disciples he's going to prepare a place for them, Jesus reminds them that they know where he's going and how to get there (John 14:3-4). Thomas, not so much "the doubter" as the guy who's willing to admit his lack of clue, blurts out that he has absolutely no idea what Jesus is talking about: "Lord, we haven't a clue where you're going, how could we possibly know the way?" It is in response to Thomas' spoken (and, I supect, the others' unspoken) question that Jesus states "I AM the way..."
Jesus did NOT say "I am starting a new religion with you guys, and this religion is the only way to avoid hell." Hell's not even part of the discussion. Nor did Jesus say "no one can be saved unless he thinks in his mind that I am the son of God and I am dying for his sins." No, Jesus says "I AM the way" directly in the context of his having just told his disciples "you know the way." The life they have lived with Jesus during the past three-plus years of his earthly ministry, the jobs he has set them to do, the miracles they have witnessed, the teaching they have absorbed; all these things wrapped together have taught them "the way" to the Father, which is the person of Jesus himself. When Jesus goes on in John 14:11-14 to encourage the disciples to believe that the Father is in him, even this is not for "salvation" the way we think of it...it's so they can do what they've seen him do and more, "so that the Father may be glorified in the Son."
Jesus' words in John 14 (really, all the way through John 17) were spoken not as a warning to unbelievers, but as a comfort to those who already believe!
When Christians loudly proclaim "no man cometh to the Father but by me," they are not talking about following Jesus. They're not talking about obeying Jesus. They're certainly not talking about staying faithful under hardship and persecution. No, they're talking about how wrong Muslims, Hindus, Buddhists, Liberal Christians, Humanists, and sundry other "infidels" are. They're usually talking about their certainty that all of the above are destined to burn forever in hell. (For a current example, take a look at the discussion on my friend Kurt's blog today!)
The gospel of Jesus Christ claims things about him that are true of no one else. Nobody else is Jesus, and no other teaching holds the stunning uniqueness of the One who rose from the dead. I am not advocating for the feel-good universalist straw man so often the target of the self-righteous quoters of John 14:6. But to properly frame those places where Jesus' words confront society, or other faiths, or the Christian church, we have got to start by representing Jesus' own words faithfully. Using John 14:6 to club "unbelievers" and universalists over the head is categorically NOT faithful to Jesus' message.