brought in a Jew
to speak in my religious school class once. He started his speech with a statement somewhere along the lines of
"I'm a Jew, but I also happen to believe in Jesus."
He went on to talk about how he's still Jewish even though he believes that the Messiah has already come to Earth in the form of Jesus Christ. He still participated in all Jewish holidays, prayed in Hebrew, wore a tallis and yarmulke to shul, and so on. Now, the question that this raised, at least in my mind, is "What's the difference between a Jew who believes in Jesus and a Christian?"
Jesus' first followers were a group of Jews who ended up believing that their spiritual leader was the Messiah. The first Christians were, um, Jews for Jesus.
You're a Jew for Jesus? You're not a Jew anymore. You're just practicing Christianity the way it was meant to be practiced at its inception.