Fisting has biblical support according the those kooky kids at sexinchrist.com
In the Song of Solomon, the Bible describes the act of fisting and the profound erotic bliss it induces: It is the voice of my beloved! He knocks, saying, “Open for me, my sister, my love, My dove, my perfect one”…My love thrust his hand through the opening, and my feelings were stirred for him. (Song of Solomon 5:2-4) Here we see the lover gently coaxing his companion to open up to him, metaphorically “knocking at her door,” preparing her sexually and emotionally to receive his hand inside her. Gradually he works more and more fingers into her, until the moment when her vagina yields and his hand slips fully inside her, thrusting “through the opening.” She then describes the powerful passion that this arouses in her as she envelopes his entire hand inside her body. Many couples describe this moment, as the fist makes full penetration into the vaginal opening, as transcendent and a sexual revelation. As the woman’s body accommodates her husband’s hand, both may experience a sense of physical, sexual, emotional, and spiritual oneness.
Apparently the bible approves of oral sex (The Living Water is taken rather literally), anal sex and all sorts of other things… who knew!