Instruments
Two with die (Flöte, Harfe), two with das (Cello, Saxofon).
Feelings
Die Freude, die Wut, die Angst, but der Stolz.
Landscape
Der Berg, der Hügel, das Tal, die Wiese: all three articles.
Things with keys
Das Akkordeon is an instrument, but it has keys, like das Telefon, die Kasse and der Computer.