I have gold in all campains and challenges. Unlocked 92%. 6 items remain locked. How do I unlock them. (Did I miss something somewhere?)

You have to find all the Easter Eggs. They are crates or locations which are hidden in the missions and tutorials. I won't tell you where they are, this is not funny :D

Thanks for the info Kilburn, Now it's time to go Easter Egg hunting. (Yes it's true, old folks don't know "everything".)