His favourite at the moment is LETTERS! We have to stop at every sign we pass (which is a LOT if you know our regular routes) so that he can read all of the letters for me.
My favourite at the moment is chickpeas! After soaking a huge pile of them I spent the afternoon playing in the kitchen. The result was a ridiculous amount of hummus (of course) and a jar of chickpea cookies (sugar-free yet surprisingly delicious and more-ish)! I made them star-shaped in a bid to thwart the inversely proportional relationship between time/effort (spent making food for toddlers) & enjoyment (displayed by toddlers when eating said prepared food) - which a wise friend once warned me about. A twinkle-twinkling success!