Leigh,
Besides the filtering method suggested above, you can also "automate" the process by defining the SHEET MATERIAL size as 1" x 1" (or similar very small size). Again, the part will show up on the cut list, so I usually use a name that properly describes the material but I tack on something like NO-CNC at the end just make it clear to those referring to the list .
When you process the TWD with Control Nesting, you don't even have to filter the parts out. Control Nesting will automatically give you a *WARNING* that the sheet material is not large enough to nest the associated component(s). You just have to acknowledge the warning and Control Nesting will skip those affected parts and continue with the rest of the process.
This method is good for ANY "No-Cut-On-CNC" materials, such as glass, marble, etc... You never have to worry about not filtering these "never-cut" parts because Control Nesting will do it automatically!
Hope this helps...