Regret, as a first off reflex choice - the soundtrack to my first summer term at uni, the track they started their set with first time I saw them. Great remixes too.
I’m going to go rogue with my second choice though - there’s so many I absolutely adore and if I picked say, Thieves Like Us, I might change my mind tomorrow. So instead my second choice is Run Wild, a track Bernard wrote for his baby daughter (who must be 17 or 18 by now), which I used to sing to Jimbo at bedtime every night as a baby and is now on his bedtime playlist of less baby-ish lullabies (and as a consequence, probably the track of theirs I’ve listened to most of all)