Xylophone - we use it in music related classes. It is easy to use for the youngest students.
Bulldozer - very useful when we are practicing our sequencing skills. We collect eggs or plow the snow.
Launcher - a very fun attachment for Dash that allows us to launch things. Our favorite: candy launch for Halloween :)
Building block connectors - we use them together with LEGO to build our own and original attachments for the robots