There's an old story about two senior architects that were friends in college, and met again thirty years later. After a few minutes they started talking about their favorite achievements. The first described office towers, airports, and universities he was quite proud of. The second didn't have any monuments to talk about, but shared that he thought he may have designed the perfect chair.t chair. Clearly trumped, his friend congratulated him, and asked to hear more - since the perfect chair is far more significant than yet another monument.
Sometimes, I feel that small unix utilities are to a programmer what a chair is to an architect: they continue to be essential, and are typically small, spare, do just a single thing and can clearly show elegance.
I've written quite a number of them, and have recently started packaging those related to data analysis into a project called DataGristle. My favorite utility of the set is gristle_slicer - a tool similar to the Unix program cut. While cut allows the user to select columns out of a file, gristle_slicer selects columns and rows - and uses the more functional Python string slicing syntax to do it.
It's no perfect chair but it might be a good utility.