3D Only Entities
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+ 3DFACE (DXF)
+ MESH (DXF)
SOLID (DXF)

2D / 3D Entities
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+ ARC (DXF)
+ CIRCLE (DXF)
+ ELLIPSE (DXF)
HATCH (DXF)
HELIX (DXF)
+ LINE (DXF)
+ LWPOLYLINE (DXF)
MLINE (DXF)
+ POLYLINE (DXF)

2D Only Entities
================
SPLINE (DXF) - a (rational) spline with ControlPoints, Degrees, Knots and Weights. 

Intermediate Entities
=====================
+ SEQEND (DXF)
+ VERTEX (DXF)

Unknown / Unsupported Entites
=============================
- 3DSOLID (DXF) - AA library objects in encoded binary format
ACAD_PROXY_ENTITY (DXF)
ATTDEF (DXF) - annotation
ATTRIB (DXF) - annotation
BODY (DXF)
DIMENSION (DXF) - annotation
IMAGE (DXF)
INSERT (DXF) - annotation
LEADER (DXF) - annotation
LIGHT (DXF)
MLEADERSTYLE (DXF)
MLEADER (DXF) - annotation
MTEXT (DXF) - annotation
OLEFRAME (DXF)
OLE2FRAME (DXF)
POINT (DXF)
RAY (DXF) - a ray with starting point and direction, extending to infinity on one end. 
REGION (DXF)
SHAPE (DXF)
SUN (DXF)
SURFACE (DXF)
TABLE (DXF)
TEXT (DXF) - annotation
TOLERANCE (DXF) - annotation
VIEWPORT (DXF)
UNDERLAY (DXF) - underlay (image) of document
WIPEOUT (DXF)
XLINE (DXF) - a line with starting point and direction, extending to infinity on both ends. 

SECTION (DXF)
TRACE (DXF) - Four points defining the corners of the trace