DD is almost 4, and her favorite thing is to "do bowling" in our unfinished basement.

DH's parents found the old plastic set he played with as a child. It's like this -- keeps her busy and is a great way to talk a bit about addition and subtraction:

http://www.amazon.com/Kids-Plastic-Bowling-Party-Toys/dp/B001L62MJO

http://www.palumba.com/product/cherry_playstand/153/?catID=102

we have this it gets many hours of play from the kids.. they all toys in and out and spend loads of time in it.

it is by far our best toy purchase

my 4 year old is getting -
a train table with trains and tracks
2 remote dinosaurs that interact
a baby you feed
various board games
some new puzzles
a wood pirate castle
and whatever else ive stuc away over the year ...

I thought about a kitchen or a wooden tool shelf set
we also like imaginext toys, he has a cool wooden fort in his room that is a HUGE hit, if you have space my son loves the zipline at his cousins, we have a easel(we prefer the little table though)

light sabers rock

Ok, well, I wasn't going to go here cause i know that there are plenty of parents who don't approve, but what about some toy swords/guns (nerf or just replica ones that don't shoot anything)?

Our DS is also getting into crafts and coloring, so I'm getting him a giant set of crayons and also a rock painting kit.

Books are another one...candy...temporary tattoos...beanbag chair...lego table...

OP here, thank you all again, unfortunately he seems to have every item mentioned, which makes me a little concerned about what is going on over here...He got one of those Vtech cameras two years ago for Christmas, another grandparent is getting him a real camera, I know don't ask. I think part of the problem stems from birthday/Christmas combo, 6 grandparents and 18 kids at his bday party.

LOVE the stomp rocket, pirate ship, books, dress up stuff, sports stuff? What about something for winter like a new sled, snowman kits? Does he like to build? What about some sort of tool set that has pieces to build things? I don't have a specific one in mind but I know I have seen them.

Does he already have a camera? My DS is getting one of the Tough for Kids cams and I think he's going to love it.

Well, DS just turned 4 and told me he wants a tractor. We also got him a couple of new games (a train one because he's still obsessed and rock em sock em robots). He has mats and cars and trucks and trains and legos galore, and we're having a hard time coming up with anything else.

For his birthday (a few months ago) we told him we'd take him to the B&O train museum. I just showed him the website and then we took him a month later. He had a blast. There's also the Maryland Science Center, but I can't remember if 4 is a good age, or if they should be a bit older.

Sports equipment is another option. Balls, bats, we have a little trampoline that DS likes (a jogging one, not even one for kids)...stomp rocket? That's usually a hit.