Mango is often overlooked, but as a medical patient myself, I find it quite useful. It gives a good stone without being overpowering ... very relaxing, peaceful and a strong 'feel-good' sensation. It's easy to grow and the plants are fairly hardy. Negatives: It's a decent yielder but not a great one. It tends to get boring if you smoke it and nothing else for too long.

Edit: You can never go wrong with White Widow, but the Sativa side definitely shows its face ... if you want total relaxing, this might not be it.