“A little less ordinary”
If you feel that the mainstream flute duet repertoire is a little ordinary then perhaps you should look at this challenging piece by the American composer Katherine Hoover. The title is graphic as the two flutes dodge round each other in both rhythm and tonality. The parts are always very close together in pitch and there are dissonances which add an interesting and evocative colour. Initially it takes a bit of working out but it really is great fun to play.
Difficulty level, roughly compared to ABRSM exam grades. 0 is beginner, 9 is advanced (beyond grade 8).