I know this is too obvious coming from me but Data Modeler is my favourite tool and I use it every single day. Without Data Modeler I could not do my work and design databases well and efficiently and without it I could not show other people how easy and important it is to design databases. 18.3 just came out and it is ever better than the previous versions!

https://www.oracle.com/technetwork/developer-tools/datamodeler/downloads/index.html

Thank you ODC for Oracle SQL Developer Data Modeler!