It is possible to use Emoji in file and folder names. When typing a file or folder name, you can choose Edit > Special Characters, click on Emoji, and add the symbols you want to use. They will display in the Finder as part of the item’s name. If you use them at the beginning of a file name, they sort above numbers but below spaces.
[kirkmc adds: We had a hint last year about using Emoji in LaunchPad. I felt it was also interesting to point out that you can use Emoji in file and folder names. Personally, I wouldn’t want to put smileys on file names, but adding symbols can make certain folders stand out. You can even add folders to the Finder sidebar, and the Emoji will add some color to that drab gray area (whereas custom folder icons don’t display in the sidebar).]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20121029072330939