scala> Nil
res0: scala.collection.immutable.Nil.type = List()

scala> Nil == List()
res1: Boolean = true

scala> Null
<console>:8: error: not found: value Null
              Null
              ^

scala> null
res3: Null = null

scala> None
res4: None.type = None

scala> Unit
res5: Unit.type = object scala.Unit

scala> val a = println()
a: Unit = ()