Okay, so it was Dementor pee.

Just finished rereading "Harry Potter and the Odour of the Penis" and it occurs to me that Harry himself may prove to be the last horcrux, though unintentional. Voldemort wouldn't have known about the one Regulus Black destroyed, perhaps returning an piece of soul to Voldemort which he inadvertantly passed to Harry when he tried to kill him as a baby.

I suspect both Neville and the Weasley twins' joke shop will feature prominently in the last book. Rowling likes her underdogs, and she was gretly insired by Tolkien. Neville may have to try to destroy Harry (out of friendship) to kill Voldemort.