DD1 has a thing for airplanes, the airport, motorbikes, shoes and bags.
She has more shoes than i do and chooses her own, she can spot an airplane from miles away and is hell bent on spending as much time as possible on our motorbikes.

Outside of those slightly boyish but normal things DD1 has an issue with bottle tops, if she finds a bottle with no lid she gets frustrated and HAS to find the lid, she also does this if she finds a lid with no bottle.
She has an issue at times with closing doors, if she walks through an outside door she MUST close it or make sure someone else does... i swear she borders on OCD at times.

DD2 is shoes, the minute she spots them she wants them on and she will continually repeat SHOES until she gets them. Oh and apples.