Question:
What is the best all natural pain medication?

Answer: That would depend on where the pain is and what is causing it. You've gotten some good answers: White Willow bark and Jamaican dogwood are both used for pain. Herbs, Etc. makes a good liquid extract for pain that has both those herbs and several others in it. Meadowsweet has salicyn in it but is more buffered than White Willow.

If you have a headache, I would start by putting a dot of Lavender oil on your temples. If it is a sinus headache, add Peppermint oil or Rosemary. (If you have a chance to lie down and close your eyes for a minute you can even put it on either side of the nose, over the sinus cavity.) If it is stress related, put a bit of the oils at the base of your neck and on the tight muscles on either side of your neck.

If you have sore muscles, I would try rubbing with diluted Birch oil. Mix 15 drops of the pure essential oil with about a tablespoon of carrier oil (almond oil). If you don't have Birch, use Tea Tree. St. John's Wort oil is good to massage on strained tendons.

Curcumin, taken in capsules, is good for chronic pain like arthritis. Yucca and Devil's Claw in combination work extremely well for this but may cause gas in a sensitive stomach.

The best alternative medicine will look for the cause of the pain and try to alleviate it, rather than just blocking the pain with an herb or supplement.