Fakie/Halfcab stuff, anything Frontside, and for me, double whips. I can do them flat every try, but I hate it because i cant catch them, and it sketches me out. I can whip bar sets though
I think doing anything with a rotation down a set is hard. Like just doing a 360, a bar, a double whip or even a decade is easy, truck drivers aren't that bad either... but 360 whips are hard as the dickins for me down a set, but I can do them flat... idk