Well, that depends on individual ideas of what is 'cool'. I enjoy almost all of my creations. Recently, however, I built a bracelet which also acts as a computer. It was a delicate process and rather challenging in some aspects. I'm rather proud of it.

I have always like creating things, so the leap from simple robots to, say, a building was more of a hop than anything. It also helps me be self sufficient, which is good in my homeworld.