A couple of friends of mine told me about this during OR and I've just had the chance to look it over - my guess is it's going to stir up quite a conversation.
Ballista Tactical Systems has released their Nautilus Rotating Rail. It's a single rail 'platform' (1913/Pic Rail) for the AR15 that actually comprises two separate and adjustable rail systems. Each section, which can be rotated a complete 360 degrees around the barrel in 45 degree increments, is comprised of four individual Pic rails. This allows the shooter to adjust the rails of his weapon in order to position different accessories as needed (such as rotating a light from one side to the other depending on which side of the door he's stacked on) without having to manually switch out any furniture.
According to Ballista Tactical Systems, all optics will maintain zero. The system locks in place so it doesn't go spinning around unintentionally and is intended specifically for carbine length gas system AR15s.
The Nautilus is made of aircraft grade 6061 T6511 hard-anodized aluminum and they advise it's been "...thoroughly tested in a variety of environments...such as water, sand, mud and grass. It is designed to withstand significant contamination and still maintain its full rotation ability..."
The description mentions that a shooter could put up to 8 different accessories on the Nautilus and use each as needed...I don't know that I can think of circumstances where I'd want to hold a rifle with 8 accessories at ready, but used circumspectly I can see how the 45 degree rotation capabilities would be appealing. That said, I'd want to see it successfully rotate after being fouled with sand, dirt or swamp before ever taking it to a 2-way range.
You know damn well someone out there is going to mount a Nautilus to his rifle and take a picture with four QD rail bayonets, a scope, a CQB optic, a bipod, a vertical grip with light and a laser-light combo.
I'd do it myself, but I don't have four bayonets and I'm not allowed to play with lasers in the house anymore since our Boerboel chased one into the television.
More pictures and instructional videos on their media page: http://www.ballistatactical.com/pictures-videos/.