One thing I think is sorely lacking is approachable documentation for writing python extensions to GDB.

I've managed to cobble together a collection of data structure explorers written in Python but it is barely an improvement over straight gdb scripting due to the way all structs end up as dictionaries. Some higher level libraries for inspection might be nice. Automatic integration with something like graphviz would be amazing. For instance, it would be cool to just describe my data structure(specifying 'next' pointers or how to access edge lists for a graph) and just have a library dump a visual representation for me. That said, I wonder if half of that logic is best left in a debug module inside the application or library where it remains more tightly coupled to the actual layout.