For a first birthday, a rattle.
Something they can grow into, enjoy for a long time and can be expanded on as time goes by.
As Minty said. Brio train set.
We bought a basic one 23 years ago. Added to it as time went by. Four of our children enjoyed it. It's still in good condition and there are other cheaper brands that are compatible with it.
Started with a basic circular track, now it can look like British Rail!!
(Maybe that was a bad comparison).
I'm sure one day grandchildren will get a lot of enjoyment from it.