Both Quest Rewards
In Ill Met by Moonlight upon encountering Sinding while he is in Werewolf form if you agree to help, you can obtain both rewards. First Kill the hunters to help Sinding, then kill Hircine and skin him to gain the Savior's Hide. After doing this you should exit the cave upon which an aspect of Hircine will appear and congratulate you on helping Sinding and uncurse the Ring of Hircine, letting you keep it.
Note: Alas, as of 2017 using the Unofficial Patch with Skyrim SE the above glitch no longer works. You will only be able to get either the Savior's Hide or the Ring of Hircine.
- Savior's Hide is a play on the term "Save your own hide"