Solution is presented as a walkthrough:
The best thing here is to decide what you like and what you don't. This close to the end of the game I offer one that not only has a humorous questline but an item that serves little purpose, both close to the end and in practicality. I chose Sheogorath's Wabbajack.
Sheogorath, the Daedric god of mischief, is easily found south of Bravil (slightly sw) or nortwest of Fort Redman, ultimately west of the Wayshrine of Stendarr. Back off the road in the woods.
The offering is simple, considering how short the quest is, yarn, lettuce and a lesser soul gem. Part of the appeal of this quest is the servants and Sheogorath himself. The acting is great and the lines are funny. After you've made the offering he'll give you instructions to create omens to the apocoplypse in a nearby town of Border Watch. This is also an easy task, bring the Plague of Rats, if you're staying in the Border Watch Inn, its also a cheese museum, with a stew pot outside. The shaman will drop rat poison at the top of the steps, killing the rats. The next prophesy says that the live stock will die. Use the remaining poison or your sword, but remember the order; rats then livestock. Talk to the shaman and he'll tell you to run "We're all doomed!" Sheogorath's voice will boom overhead, return to the shrine and grab your brand-new Wabbajack.
What is it you say? Why'd I trade it you ask? Its a staff of transmutation, it could change a Daedra into a rat , OR a rat into a minotaur. You have no control over which.
And moreover, Martin tells you whatever artifact he uses will be destroyed, no way out of it. A list will pop up with all artifacts in your possession and he'll ask you which will you sacrifice. The nifty key? That wonderful sword? I chose this because I still plan to meet Sheogorath in The Shivering Isles.