Have GTO.

1. Flags - I use two of different shapes and colors.
2. Lights - bright, flashing, potential for day and nite.
3. Clipless pedals and shoes
4. Rear view mirrors.
5. Cargo rack bag to carry a few tools, tire patch kit,...
6. Water bottle holder, if you want it in easy reach.

I like my headrest, but it is not a necessity.

73/gus