The best software modeling tool which I've ever used is Power Designer from Sybase.
I've got acquainted with this program some years ago (it was a repackaged version "QDesigner" by Quest Software).
I've really enjoyed developing with this tool.
This tool is very useful and usable, flexible, easy to use and pretty good.
Power Designer CD contains some visual samples.
Object Oriented Model
It is possible to create UML diagrams (classes, sequence, deployment, etc.) and generate source codes (for many programming languages) from the model.
Physical Data Model
Development of a database turns to pleasure. Power Designer can generate SQL scripts with databases and tables definitions. Also it can create test data sets.
I've tested and evaluated some trial versions of Power Designer and I may say "it is the best".
You may download free evaluation copy of Power Designer or buy it.