Reflectors are substances that reflect waves (sound, light, etc.). To "reflect" means to "bounce back". Likewise, poor reflectors are substances that do not reflect waves.
Shiny and smooth surfaces tend to be characteristics of good reflectors of light waves. Such surfaces cause light to bounce (reflect) at the same angle in which the light hit the object. Rough and opaque surfaces are characteristics of poor reflectors of light. Such surfaces cause the light waves to scatter.
Therefore, substances that could be listed on the "good reflectors" side of your table are: metals (aluminum, copper, silver, gold, spoons, etc) and mirrors.
On the "poor reflectors" side of the table, the following items could be listed: cotton, paper, carpet, jeans, concrete, and grass.
Below is a lab that you may want to perform in order to prove the claims made above.