My students enjoyed the opportunity to build with legos in our Scale Factor Unit. I had them measure their towers and we used there real measurements to find scale factor and practice using scientific notation.
Another surprising hit was using pattern blocks as a formative assessment of Line Symmetry and Rotational Symmetry. Most students immediately did well with line symmetry, but rotation symmetry was a new concept. Using blocks that were easily movable helped students remember the concept and calculate angle of rotation. After only a few times practicing with the 3D models, most students could apply the concept to 2D pictures.