Wait, there's more : Obfuscation
Last week, I linked to DrIntl's idea to make passwords more difficult to guess. FYI, Michael Kaplan commented about it as well.
I18n used as an obsfuscator
Speaking of Michael, some time ago, he mentioned another interesting side effect of i18n : In languages such as C# where identifiers are not limited to 0-7F ASCII chars, using diacritics in identifiers names can lead to some fun results.