Well... here's a list of object types to get you started.
Duct, Duct Fitting, Duct Custom Fitting
Pipe, Pipe Fitting, Pipe Custom Fitting
Conduit, Conduit Fitting
Cable Tray, Cable Tray Fitting
Plumbing Line, Plumbing FItting
Hanger
Device
Panel
Wire
MvPart
Labels
Schematic Line
Schematic Symbol
To get the DXF name, just insert an instance of each, and use the LIST command.
Of course, there are all the ACA objects, as well as the AutoCAD objects. There are also all the styles that aren't 'drawing' objects, such as:
Duct System Definition
Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.