The dwg format is the abbreviation for Drawing (in French: dessin).
This format is the most common CAD and CAD file.
Here is the list of software that uses the dwg format (as native format):
Autocad
GstarCAD
intellicad
Iplus Concept
ZWCAD
Microstation
DraftSight
MENSURA GEODES
MEDUSA4 Personnal
bricscad