While answering a few questions, I've wished we had MathJax enabled on the site. It's a JavaScript library that displays mathematical notation in web browsers, using a couple markup languages including LaTeX.
The wishing hasn't been motivated by a desire to write hideous math equations (which I don't think the audience would care for) so much as some basic stuff that might complement the text.
What we've got works quite well, but given that the feature is installed on a number of other SE sites, I'm wondering if it'd be as easy as flipping a switch.
$\S$
, which is nice for those of us without a keyboard shortcut