1) Blocks: My mom bought Justin a set of Melissa & Doug wooden blocks and Justin played with them so much that I bought a second set. Ryan likes them too, but Justin plays with them every single day (unless I have taken them away). He builds things for his dinosaurs, for the little people animals, and for other figures. He makes towers, machines, and things that I have no idea what they are. Great investment, classic toy, last forever. Gotta have blocks.
2) Trains: Let me start out by saying that I hate Thomas Tank Engine. I was able to find some great deals on cars, tracks, etc. and slowly gave in. Justin had seen them at other people's homes and loved them. Ryan loves them even more. Now that we have more track pieces, even Rob and I enjoy putting tracks together. We often have creative differences with Justin though.
3) Fisher Price Little People/Animals: We have a few different sets and the boys just LOVE them! They play with the little people and the animals all the time, often without the main set part (barn, airport, etc.). Justin acts out all sorts of things with them, while Ryan is more interested in manipulating the objects. He loves to stick the animals down the silo and watch them fall out the bottom. He also likes to collect the "moos" and other favorite animals and make sounds for them. Best of all is to destroy things that Justin has made.
I know that in the picture below it looks like they are playing nicely beside each other. Please note that lasted all of about five seconds before Justin just HAD to have things that Ryan had or Ryan HAD to knock over the figures that Justin had so carefully placed in just the right position.
4) Legos: Usually the Lego creations are not as big as this one. Justin wanted to make something that was 100 Lego pieces tall. These are actually Duplos. There are a few MegaBlocks mixed in (cool TV cartoon characters), but I primarily went with the real deal. After purchasing a few, I saw how much Justin loved them and bought a ton off of eBay and was thrilled with the deal. Kids outgrow the larger Duplo faster than the normal sized Legos, so I didn't want to spend a fortune on them. Justin and Ryan both have a blast with them. Typically, Justin will build something for the Duplo cats or the Duplo dinosaurs. He loves to make them little houses or playgrounds. He will also build other things like towers. He enjoys taking the basic blocks and making color patterns too. Ryan was at the stage where he primarily knocks over things that are built or pulls pieces off of structures. Now he can build things (okay, not really things, he is just hooking them together) and he thinks he is soooo cool. I think so too. Justin wasn't able to do that at the same age. Of course Justin hadn't had the Duplos for long at that point and Ryan has been around them since birth.
5) Stacking/Nesting Cups and Boxes: Okay, in this picture he isn't stacking or nesting, but he does love the blocks as well as the stacking/nesting cups. When Justin was this age, he had cardboard stacking blocks. They eventually came to an end. I found these wooden ones and thought they would be much more durable. They are, but they hurt when they hit you. Justin and Ryan have managed to break one too, but it wasn't hard to repair. These things are inexpensive, need no batteries or assembly, and provide hours of fun. They are also fun to fill up with smaller toys or to serve as little garages or houses for things.
Dinosaurs, wild animal figures, cars and trucks, play food, battery powered abc or music toys, stuffed animals and dolls are all fun too. The boys have lots and lots of toys. I try to rotate them so that they are not all out at once. That makes it easier at clean up time and means that they are excited to see something that has been put up for awhile. I don't put away the top 5 toys unless it is a punishment for misusing them (ie throwing them or using them to hurt each other). Then they are only up a night or two. I do rotate the little people buildings and accessories, but leave the people and animals out and available.
Justin is creative and combines a variety of different types of toys. That's great, but it means I can't really tell him to clean up all of one thing before getting out another. Chances are he is playing with both (or all)! Here he is with blocks, beanbags, a scarf, Fisher Price little people, and an empty container.
I have also found that with clearly labeled bins, shelves, and containers, that even Ryan knows where things belong and can help clean things up. It also speeds up clean-up after play dates as kids and their moms can see what goes where. You can use actual photos, jpegs from online, drawings, words, etc.