What other text is rendered as a symbol or icon besides [] and [x]?

Just discovered that the Data Grid / Table does another cool and unexpected thing -- adds checked or unchecked boxes when you include [] or [x] in the text box. Are there other such symbols or wingding kind of things lurking about?

Especially for column headers, it would be great to display a upward or downward pointing triangle to indicate a column is sortable, and if the sort is ascending or descending.

Cheers,
-- Joe