Here's the list of electronics I carry on any given all-day mixed-terrain ride. It's getting a bit out of control. And it requires too many electrical wall outlets and a tangle of cables; if I were to charge all these items at the same time it would require 14 outlets. Therefore, I have to charge everything in stages, particularly when traveling.

My primary bike also has a generator hub, generator light, and Sinewave USB charger. Regardless, I still carry all the lights and batteries mentioned below.

Will Not Ride Without

GPS Device: Garmin 1000
GPS Device: Garmin 810: I always ride with a backup GPS unit. I've had too many adventures where my Garmin ended up having a major issue. The backup unit provides me confidence to head into the woods without hesitation. And, my phone is my third backup - or fourth, see below - so I have no worries. I have other GPS units but this combination I find to work best in most cases.
Phone
Battery backup 5,600mAh.
Battery backup 12,000mAh. Three reasons I carry a second larger backup battery:
1. In the winter, battery life gets reduced by up to 75%; I've been on rides where my Garmin dies after about 3 hours.
2. When I'm riding with other people I find this backup has come in handy a number of times.
3. If I have a mishap and will end up being outside throughout an evening, this backup will keep some items powered through an unexpected additional 10+ hours of dark.
Headlight: Light & Motion Urban. I typically use this for my helmet mount. No better light placement for night riding in the woods - so you can see around a corner, or for urban riding - where you want drivers to see you.
Headlight backup: Light & Motion Gobe 700. I've found that the only truly waterproof light is the Gobe. They're cumbersome for helmet mounting, and for riding in general, but being stuck in a lightning storm at 2am on the trails without light is not something I want to live through again.
Headlight backup: Light & motion Gobe 700. I carry enough lights that I can ride throughout the night without running out of light - regardless of my generator light. I've had my generator system die on me once; don't want the ride in the dark again.
Taillight: Clip-on to jersey pocket. I use a battery operated taillight, not a USB chargeable. USB chargeable don't last long enough.
Taillight: Small mounted to helmet tail.
Electronic shifting: If you have Di2 or eTap electronic shifting, make sure you do a full charge before any big ride. With eTap make sure you check the brifter batteries, too.

Vanity Items

Items I pretty much always carry on all-day rides, but that I don't really need.

Camera: Sony RX100 III. Note: For the photo above, I used this camera so I had a stand in - that's why the 'camera' looks a lot like an external hard-drive in this photo.
Video Camera: Garmin VIRB or GoPro 4.

Don't Like Riding Without

These are items for other riders, or I'll bring if the weather or riding conditions indicate it.

Foot Warmer Batteries: In temperatures below 20 degrees I'll typically wear Hotronics FootWarmers.
Third backup GPS device: Garmin 800
Video Camera Backup: Either second VIRB or GoPro 4 - or both.
Headlight backup: Light & Motion Urban. If you're counting, this is the fourth battery operated headlight I carry. While the Gobe is more water-resistant than the Urban, the Urban is a better helmet mount headlight. I've never killed an Urban in rain during its first charge. However, if I'm doing multiple days in the rain, I expect the Urban to have issues; I'll keep it well protected from water until I need it.

That's about it. Charging all this stuff takes a while; I better get started.

What electronics do you carry for your long rides?