Currently building a triple chainring shifter bike after retiring my old bike. The handlebars will be the last thing I put together. When I'm done this will be on my bike:
Bicycle computer (speedometer)
Tachometer/hour counter
Mirrors
Directional lights controller
Head/tail light
Kill switch
Horn
Twist throttle
Trigger shifters.
Cellphone holder/charger
Here's an old setup I had when I first built my auto shifting bike.
View attachment 103506