I think probably the most interesting part of the tour of Edinburg castle was being able to see the Honors of Scotland, which are Scotland's version of the crown jewels - consisting of a crown, a sceptre, a sword. After Scotland unified with England (Union Act, I think), they actually locked the honors up, since basically there was no longer a need for them, and would probably just be a reminder to everyone that Scotland used to be its own country.
There is also a stone called the Stone of Scone in the Crown Room, which was used as a throne for the crowning of the earliest Scottish Kings. Funny thing is that it's been under the throne of England until only a couple of years ago.
