I'll give you three just in case a couple are ones you aren't quite looking for.
-Carbon has several allotropes, or different forms in which it can exist. A couple of allotropes included are graphite and diamond, which both have very different properties.
-Despite carbon's ability to make 4 bonds and its presence in many compounds, it is highly nonreactive under normal conditions.
-Carbon exists in three main isotopes: ¹²C, ¹³C, and ¹⁴C in which ¹⁴C is radioactive and used in dating carbon-containing samples (known as radiometric dating)
Hope this helps!!