I am often surprised by how little use my fellow Unix admins make of hard links. It may be because their presence in our file systems is so much more subtle than their soft (i.e., symbolic) link cousins, but if you like the idea of a file just showing up in a second location without the overhead of additional disk space, hard links are very effective.
A hard link is, basically, another instance of a file — not a copy and not a reference (as is a soft link), but another appearance of a file. It can be in the same directory with a different name or somewhere else in the file system by the same or a different name. If you pull that off as a person, it would like being in two places at the same time. I often wish that I could do that myself!