In my last school all teachers did a year long research project. I did a project about using Lego in the middle school classroom, with Michelle Jones (who is now working with me at my current school!). We did some things together and some things separately. Here are things I did, or did with Mich:
I felt inspired after looking back through our work and decided to create a mini Lego activity to use with my students...partly inspired by the Extraordinaires, partly by the duck challenge and lastly by Lego activities I have done at trivia nights, or at the Museum of Design Atlanta's Bricks and Brews Nights. In fact - here is an example - I went to Bricks and Brews, and our prompt was 'cartoons' - we made a Cat Dog model!
The following challenge can be done as a warm up activity, or can be extended to last for a whole class period. You will obviously need Lego Bricks, (though if you don't have many, you could make the challenge harder, by giving them a limit to the number of bricks they could use)! You can give all students the same product to design, then they have to justify their choices, (Optional: Students can vote on their favorite Lego creation / or students get to redesign their product after getting ideas from their peers). The other choice is giving each student a product secretly, then having them design it, then the other students guess what it is. I recommend printing out the presentation, with 6 slides per page, then you can cut products out, and hand them out as little cards.
Here's a link to the presentation. Feel free to make a copy and adapt it (File>Make a Copy).