DaisyDisk is very polished and nice, but I'd like to add GrandPerspective [1] to the discussion - it's not as pretty, but it's free and does a very good job as well.
If you don't mind spending $9.99, DaisyDisk is definitely worth it, though.
GrandPerspective is a quite delightful disk space visualizer, and was the app I used to replace the delightful workhorse 'Disk Inventory X'[0] since Disk Inventory X was infrequently updated and would routinely become incompatible on new OS X versions (this was almost 10 years ago).
[1] https://sourceforge.net/projects/grandperspectiv/