Not so long ago I was a frequent user of the "at" command on my server for a probably not so common task: Sending mail to myself on some random point in the future ... 400 days +-200 or something.
That was quite cool actually ... getting reminded of past moments unexpectedly,
keeping the grand picture of things alive, stuff like that.
Also sent quite a few of those to girlfriends ...
Only problem was that because I usually didnt think of the whole setup I forgot
those when reinstalling the server or the data was lost in disk crashes etc.
So with a lot of old mails lost I kinda gave up on the whole thing
while still having fond memories of it.