Rabbi Natan on the position of the Earth among the stars: Pesachim 94a
Rabbi Natan told a mother to wait for her child to mature before Circumcision, and this saved the child's life where his brothers had died; they named the child "Nasan the Babylonian" in his honor: Shabbat 134a [2x]
Rabbi Natan asking Eliyahu haNavi what Gd was doing during a particular talmudic debate: Bava Metzia 59b
Rabbi Natan asked Sumchus a question, and he replied, "I haven't heard": Ketuvot 52a