I agree that it should be called something in line with the characters and theme of the story. For instance, if it's a magical world maybe Lustful Wand .
But I kind of stick with member, cock, dick, monster yada yada yada. Playgirl did have an article quite some time ago that had a whole list of names like Pike of Love, Horn o' plenty, monster muscle, and Kingpin amoung others.
I say just use what you think is right, if after you've read through your story and you're happy with the amount of times you've used a certain word then go with it. Sometimes I think people aren't happy unless they have something to bitch about.
Good luck.