CreativeBits: OS X: Typing special characters
I wonder about the Mac developers who get stuck doing these utilities. Here's another clever one that's utterly buried in a completely obscure location and probably known to only a dozen people -- yet if you search it out it's a great way to see the effect of using modifier keys and to examine various fonts. The one downside is that it uses yet more space on the menubar, but it's good enough to warrant taking something else (the MacClassic icon?) from the menubar (command-click then drag off menubar* -- but restoring icons to a menubar is application dependent).
One of the most interesting tips I've seen in a while.
* This is one of the more obscure user interface behaviors in OS X. A Ctrl-Click should show a "remove" item on the context menu.