I love Db major chord, and I also love running up and down the keyboard with the notes Db, Gb and Ab, like the tonic, subdominant and dominant of Db major, just randomly playin reallllly fast up the piano, Iunno if I get frustrated Ill do that. And I find the hardest scale in fast contrary motion is C major because as said earlier, no clues... I also detest Arpeggios in C major.. I find the easiest scale Gflat major though, after years of practicing each one...