DBeaver - DBeaver - Universal Database Manager and SQL Client.
SQL Developer - Oracle SQL Developer is a free, development environment that simplifies the management of Oracle Database in both traditional and Cloud deployments.
DataGrip - Tool for SQL and databases
SQuirreL SQL - SQuirreL SQL is an open-source Java SQL Client program for any JDBC compliant database
SQLTools++ - Home of SQLTools++
HeidiSQL - HeidiSQL is a powerful and easy client for MySQL, MariaDB, Microsoft SQL Server and PostgreSQL. Open source and entirely free to use.