MySQL - The world's most popular open source database
DBeaver - DBeaver - Universal Database Manager and SQL Client.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
DataGrip - Tool for SQL and databases
SQLite - SQLite Home Page
HeidiSQL - HeidiSQL is a powerful and easy client for MySQL, MariaDB, Microsoft SQL Server and PostgreSQL. Open source and entirely free to use.