Mine is “Not Afraid” by Eminem. For me and my boyfriends almost 4 year relationship, probably Am I Ready by Lizzo and Hello by Adele (even though adele's hello song is a breakup one, its still calm and it reminds me of how me and my boyfriend work things out when times are rough) (these two songs played when we went on one of our first dates and I loved it so so much still do <3)