13 Dr. Cleaner
When it comes to Mac maintenance, there are several tiers of usability (and price). Dr. Cleaner is a great option that combines some powerful and intuitive features for free.
Some of its features (like duplicate file finding) are reserved for the paid Pro version, but Dr. Cleaner sports a good toolset in its free-to-use iteration. You can easily run a scan to find hidden “junk” files that are clogging your machine, including caches, logs and temporary files that are hanging around a bit longer than they should be.