I’m always amazed what people can build from Lego. Here’s a bunch of Artoo’s I found on Flickr
This full size Artoo is from an FAO Schwartz store somewhere in the world
I’m pretty sure this one from Comic-Con 2007 is the same design
This one is from Lego Land in California. The dome rotates, it lights work and it makes the familiar R2 sounds
Then there’s the droid development kit from Lego. I still have one myself in a box that need to be built up one day.