The idea here is to be able to shut off all the lights on the bike with one quick flip of a switch. Hmmm.... why would anyone want to do that? Well, of course this is not for use on public streets, for show purposes only. Hee hee. 
I haven't tried this on my bike yet. There's really no risk to giving it a try -- you won't hurt the bike. But if you blow your nuts off with a soldering torch 
, or switch the lights off while riding a wheelie at 120 mph and hit a tree, I'll completely disavow any knowledge of this website and the GSXR itself. 
.
This is also completely illegal, as any idiot would know.
So unless you're Bill Clinton and can change the legal meaning of the word "is", you'll get some serious jail time for shutting your lights off while on the street...as if I should really have to say any of this 
, but that's life in a country where lawyers outnumber cockroaches.
The message: Don't come looking to me for a lawsuit, nor for a nut transplant. Be careful out there!
Nothing tricky here, but several riders have emailed me with questions on this idea, so I thought I'd finally make a diagram. This is the easiest way I could think of to accomplish the task...
I'd recommend tackling the headlights by putting a SPST switch directly in the white wire that supplies them. You'll need an SPST switch with contacts rated at about 8 amps or higer in order to handle the large current load of stock headlights. Then use a signal wire AFTER the SPST switch to power a relay coil, as you see in the diagram.
Now go to the tail section and cut all the ground wires to any lights you want to shut off in the tail section. This includes the tail light, brake light, any running lights you have, and your turn signals. Don't cut their power wires, only their GROUND wires, so you make sure they have NO pathway to ground.
Then connect all those tail ground wires together -- tie them up and solder this "unified ground wire" to a 16 - or 18-gauge black wire that you can connect to the SPST relay as shown.
Make all the other connections as shown and you should be all set.
Now let's follow the diagram, and the reasoning behind this to see how it works. When the LOW beam (white wire) is getting power, the relay coil will be activated, allowing the relay contact "87" to be continuous with "30", and thus the tail lights will have their ground connection, so they stay on.
When the LOW beam lights are turned off by opening the SPST switch, the relay coil is de-activated, so that "87" is no longer continous with "30", and the tail lights will go off because they have no ground connection.
Click on the image above for a very large, readable version of the diagram that will explain in detail how it works.
If you'd like to instantly switch from HIGH beams to all lights off, then you would put the SPST switch into the YELLOW HIGH beam wire, at the location marked by the red star.
With the SPST switch closed, your high and low beam selection, using the left handlebar thumb switch, will function normally, as on the stock bike.
This modification requires the use of two high-current diodes, as shown by orange triangles on the diagram.