FlameRobin - FlameRobin is a cross-platform, open-source database administration tool for Firebird DBMS.
Open DBDiff - A database comparison tool for Microsoft SQL Server 2005+ that reports schema differences and...
DBeaver - DBeaver - Universal Database Manager and SQL Client.
Redgate SQL Data Compare - Use Redgate SQL Data Compare to compare and synchronize static, lookup, and reference data in your SQL Server database - try it free
Firebird Maestro - SQL Maestro Group vendors powerful database management and web development tools for MySQL, Oracle, SQL Server, DB2, SQL Anywhere, PostgreSQL, SQLite, Firebird and MaxDB.
a7 SqlTools - Tools for MS Sql management with search, explore and comparison functionality.