* revsets -- feature-rich DSL for querying your history, my presentation on them:
* templates -- the output of just about any hg command can be customised:
* Evolve -- safely rewrite commits as a team, a safe replacement for `git push --force`:
* Very easy to write extensions:
* Mercurial scales well to gigantic monolithic repos:
That's all I can think of for now.
I hope you were able to pay attention to the talk instead of the gimmick.