I need a Diagram Tool with ability to extend set of diagram types and diagram primitives and save them as templates for future use. User-scripted exports or export formats for my diagrams would be nice, too.
For example, I want to make something like this in my game programming: http://www.bigbluecup.com/yabb/index.php?topic=38322.0
Now I use great UML-only RationalRose-like editor StarUML. It is very comfortable, stable and I like it very much.
I can think of some options:
Would any of those help you out? TikZ has been my choice for diagrams since I found it. I don't know if there's anything you can't do. Check out the TikZ examples page. Sorry if I totally missed what you're looking for and provided silly suggestions!