We got a secondhand play gym from ebay when Yasin was about 18 months old and he still plays on it. Sometimes I chuck a sheet over it to make a cubby.
Other than that we just have balls, a sandpit, a bubble blower and a blackboard.

ETA - what a doofus, how could I forget the ride on/push along car and the foot power trike. Both boys love these toys they chase each other round the garden on the for hours.