Guy Steeles Talk on Fortress reminded me on the possibility of using Unicode characters in strings and identifiers in most current programming languages.
That also opens the way for using them in DSLs. Either in internal or external ones. If the special symbols have already a defined meaning in the domain (perhaps as part of a standard notation) this should make DSLs even more readable for the people with the domain knowledge.
All that came to my mind when talking with Dan North about the great new JBehave 2 BDD Framework for Java. When parsing and converting scenario step text tokens, the usage of unicode symbols could improve conciseness and readability.
From Sam Aaron I learned that a ton of unicode characters is just an (ALT-)Keystroke away on a Mac keyboard. He also showed me that in Ruby Unicode is no problem for identifiers and string content.