Ask HN: Examples for end user software hacks/repurposing

Which end user software hacks or repurposing have you seen or used yourself? I'd like to collect some examples, be they private, or even more interesting, department or company-wide. A classic one is using excel as a database.

My intension is not finger-pointing users’ ignorance of "right" tools, but how people come up with own solutions (ideally, you can give some context around problem and solution).