usql - Universal command-line interface for SQL databases
DBeaver - DBeaver - Universal Database Manager and SQL Client.
Open PostgreSQL Monitoring - Oversee and Manage Your PostgreSQL Servers
MySQL Workbench - MySQL Workbench is a unified visual tool for database architects, developers, and DBAs.
Errbit - The open source error catcher that's Airbrake API compliant
Sequel Pro - MySQL database management for Mac OS X