While building some templates I wanted to show articles in order of popularity (based on comment count). get_posts() is really handy for this kind of stuff, but unfortunately it does not support order by comment count, so a separate database query has to be made manually (or you have to modify core files)
Since the comment count is in the wp_posts table I guess it would not be a huge hastle to implement this into the wordpress core and it would be a big time saver for me in some cases.
I hope some of you also would like this, this is my first idea here :)