Other people have given actual answers, so I'll go ahead and give the non-answer of... use psql instead!
Like Dimitri Fontaine says early in the Mastering PostgreSQL in Application Development book mentioned elsewhere in this thread, psql is really powerful. From the \d meta commands to inspect anything and everything in the database, to the variable substitution, nothing beats editing sql in your preferred editor and hitting \i my_query.sql in psql to run it. You can also nest additional \i my_other_query.sql commands inside the files you run with \i, which I've found really useful for repeatedly dropping / installing test tables / views, or setting up test data, before running the query I'm actually interested in. Take the time to customize it by adding a few lines to your .psqlrc file, like \x auto, and \timing and it becomes very usable very quickly.
I used psql for a number of years, then joined a new company where DataGrip was the norm. I gave DataGrip an honest try to see what I might be missing from a GUI SQL client. After a year of using it exclusively, I slowly found myself migrating back to psql and can honestly say I don't miss anything.
But it's also possible I just haven't tried the right GUI client yet. Anyway, I hope you find the PostgreSQL client that works for you!
Postico is fantastic. I’ve been part of a few discussions on github with new features they are adding in and the core team is super helpful and open to making the product better. I use it daily.
Postico is nice but gives me anxiety. I don't like the metaphor of browser-style back/forward yet hoping the software remembers the state of a window when you go back to it.
My money is on DBeaver (free). The killer feature is that you can have all the queries you're doing laid out on the same place and execute the one you want as pleased, and also selecting rows of results and generating an `INSERT` statement off them.
We moved from pgadmin to DBeaver at work and have been pretty satisfied. It's based off Eclipse, so benefits from the windowing/panes, and being able to use any eclipse plugins. My db usage world changed the day I got vim support and auto complete in my query editor.
I definitely meant that as "being based off Eclipse it comes with these advantages, but caveat emptor otherwise". Honestly I use Eclipse for all my Java dev at work, and compared with the OSX implementation of PGAdmin III, it's well worth the shortcomings.