What is the best medal you can get?

The only decent obtainable medals that I use are the Mushroom Kingdom medal and Quest Specialist medals (and now the Silent Crusade medal).

There are also three medals that can be obtained from doing Capture the Flag now. I'm not sure if they're only available for a short event, but they can be obtained rather easily and give +3 to all stats. There's one that requires the player to kill the five people that are carrying the flag, one that requires the player to capture the flag enemy flag a total of five times, and one that requires the player to pick up a dropped flag a total of ten times. While these don't top the Silent Crusade medal, they are easy to get and give almost the same bonus as the Quest Specialist.