Cause and effect toys? Pop up pets, shape sorters, car tracks. Anything that gave a 'reward' if you pressed a button or a dropped a ball in? My DS would scatter toys about but wouldn't play imaginatively with them. For the dolls house, he'd open and close the doors and ring the door bell and slide the dolls down the roof, but never got the dolls to 'do' anything.
As above, he'd still be mouthing toys, gravel, sand, snails at 3 and 4. He'd chew clothes, collar and cuffs!
He absolutely loved computer games. He'd run about in a circuit around the house, banging the front door. Light switches on and off, doors open and shut.
He'd watch the same scene on a video over and over, never getting bored of it but never wanting to watch the whole story. He loved action songs on children's programmes. No functional language until 3 1/2 or so, although he could identify a square, triangle, circle, cube, cylinder, sphere etc! He couldn't say drink, or biscuit or wee wee.
Eye contact fine as a baby, losing it at 12 months, gone by 18 months, back by 5 or 6 yo.
Hopefully some of this will help you. 