Well, this is naturally the least-expected feature in Second Life, but it still appeals to my poor aesthetical sense: Second Life in wireframe mode 🙂
According to legend, it was enabled on primitive versions of Second Life, then was moved just into the Lindens’ “God Mode” for a long while, and made a re-appearance on 1.10.3. Interestingly enough, people might been using it so much, that they found a tiny bug which was quickly fixed on a very minor patch today.

Van Gogh’s Matrix