Good for short tags in templating languages like PHP, e.g:
<form>
<input type='radio' name='gender' value='m' <?=($gender=='m')?"checked":""?>>Male
<input type='radio' name='gender' value='f' <?=($gender=='f')?"checked":""?>>Female
</form>
Good for switches in javascript/jQuery:
var el = $("#something");
$(el).is(':visible') ? $(el).hide("normal") : $(el).fadeIn("normal");
Good for assignment, especially where a particular variable name can take different types:
$var = ($foo->isFoo()) ? 'Success!' : false;