Helmet that can be seen from orbit (which you have seen, eddie). SOLAS tape. Bike is stock because it's not nearly as noticeable as my head, which is higher up and more prominently visible from both front and rear.
From the rear, most of what you see on the bike is the undertail and back tire. From the front, the headlight washes things out. My head sits above it all and is closer to a driver's line of sight.
Last year I also added neon gauntlets. I'd apologize for the rude gesture, but ehhh... f*ck it.
I had a Wolo Bad Boy horn on the Ninjette and it was super-effective, but can't find a place big enough on the GSXR to mount one.