notifo is a notification service that you can link your account to.
showdead gives you the option to see posts of hellbanned users (which are usually invisible).
noprocrast and the following two are a neat feature to lock yourself out of hn after maxvisit minutes for minaway minutes (to stop procrastination, as the name says).
noprocrast works very well. As someone how has a HN 'problem' I would not be able to come here if it was not for noprocrast.
noprocrast must have been a technical feat. It will enforce the limit even if you are logged out and on an entire different network and switch browsers. I have not investigated how it works (I do not want to know how to avoid it) but it works better than cookies would.