iStat Menus - gives nice menubar system monitoring panes
Soulver - notepad/calculator hybrid. great for working out thinky problems that involve math
GrandPerspective - disk space usage management/visualization. There's prettier options but none as quick and straightforward.
Postico - Nice GUI for postgres
Turn on hot corners for multitasking. Throw your cursor in a corner -> see all open apps/windows/desktop. (Used to be a default but now it's more hidden.)

For development? I just use VSCode and the default terminal with zpresto. (Though i switch to Nova for basic build-less html css/js stuff. It's a nice native app as all things Panic are.)