nvALT vs Disk Inventory X

nvALT has a simple text box at the top (similar to that of a web browser) and when you start typing inside it, nvALT immediately displays a drop-down box of all the notes that contain the text you are searching for. The more you type, the more the search is narrowed down.

Has built-in support for MultiMarkdown 3.

nvALT is not only used for simple text editing but also as a powerful tool for taking notes, TODOs, phone numbers and every other piece of information that can be stored in a plain-text file.

This is because nvALT is not designed only as a tool to write text, but also as a powerful search and organize tool for plain-text files.

It is absolutely free and released under the GPL.

This way you can find what is taking most of the space.