The foreskin of Jesus of Nazareth.
There are ample representations of Christ’s circumcision in art, and though we might blush and wince from the mere mention of the procedure, the faithful in ages past were less inclined to look away. The cult of the relic of Christ’s alleged foreskin was the occasion for pilgrimage with rival claimants to the real thing vying for the attention of the crowds and the Church’s approbation. It was a cultural icon with enough traction behind it to warrant Voltaire’s sneer, and as Modernity advanced, for many in the Church, the foreskin relics and their cults became a source of embarrassment. I think that the last one of these alleged relics was kept on display until the early 1980′s. The bejeweled reliquary and its relic have since disappeared.
That should have warranted a Monty Python sketch all by itself in Monty Python & the Holy Grail and Monty Python's Life of Brian, both. Shame they never did it.