Mine loves stacking up blocks recently. He has a tower that has 10 pieces and he spends even 15 mins trying to build it himself. Other than that any cars, the bigger the better, football (he started kicking it and running around with it) and the "that's not my.." books (he has like 15 of them already)
Blocks to stack, Duplo/Megablocks, cars, football and goal, books, jigsaw puzzles, colouring book and crayons, tricycle, teddies (he roleplays feeding them, brushing hair, putting them to bed etc.), household items like the hoover, dustpan and brush, wooden trainset.
Have you tried reusable sticker books? My 19 months loves them and keeps him engaged for a while. You can buy a range of different themes on Amazon!