We made a cardboard house out of the carseat box. He still loves to play in it at 3.
Cardboard box ramps for the matchbox cars.
Wooden trains with tracks were big at 2.5... The track is really just a free form puzzle.
Puzzles, block buddies, Magnetic Mighty Minds
Balance bike, ours is a much loved Stryder
Mini trampoline is much loved here
Musical instruments... Guitar (mine), piano, shaker eggs, jingle bells, recorder, tambourine
Museums
Books, lots of books... Content definitely matters. My son loves books with small details in the pictures, lift the flaps have long been a hit, and stories aimed a couple years higher. If a book is too simple, he just isn't interested.
Helping to cook, smelling spices
Parent tot gymnastics classes are a hit here
Swimming, music classes, and story time were fails here due to age limits, too much repetition, and unwillingness of adults to leave a script or field questions from a curious toddler. Individual teachers make all the difference though, so definitely recommend others try.
Gear magnets for the fridge. I bought ours from Lakeshore Learning after not being able to find them elsewhere.
Magnadoodle