Florida_bound (FB) described the zipper pouch attached to the strut of her trike and all the things she carried. She commented on how handy it was and how much stuff it could hold. My thanks to her for the comments. It gave me the idea to start another discussion since it's an important consideration when riding a trike.
If you're riding where you can easily call for help/rescue then carrying a lot of stuff is not as necessary; however, some things like FB described are necessary such as ID, insurance cards, meds, sunglasses, and so on. Everyone's needs are different. Zipper pouches come in all different sizes and flavors. Let's explore the topic for the benefit of new riders.
There is a zipper pouch underneath the seat of my Catrike (It's a Catrike thing) where I keep a multitool and a baggy with business sized "meet and greet" cards I created in MS Publisher. When I meet and chat with other trikers I give them a card that has my name and email address. I'm not a Chatty Cathy but I do get into some interesting conversations on occasion. People are interesting and I like to hear about their adventures. I like to see what trikes they're riding and how they have outfitted them.
Since I go on longer rides, out on the trails among the cacti and venomous critters, I carry a lot of stuff in my trunk bag. Most important is repair stuff: 20" and 26" tubes for my Dumont, a patch kit, a CO2 inflator, spare CO2 carts, a chain tool, spare chain links, pliers, screwdriver, and vinyl gloves. If you're away from home/vehicle (for me maybe tens of miles) and you have a puncture or a broken chain you need to be able to do repairs. You can easily walk a bicycle, but not a trike. With my Type 2 Diabetes walking a long distance is very painful.
I also carry extra water, snack bars for myself (but I can share). As a former first responder I carry some basic first aid materials: glucose liquid, aspirin, ACE bandage, pressure bandage, band aids, antibiotic cream, adhesive tape, tweezers, scissors, small razor blade cutter, a cigarette lighter, and a foil type emergency blanket (keeps someone from going into shock), etc. You never know what you might run into on the trail. I want to help others (including those fast moving, obnoxious cyclists who may crash into a Cholla cactus) if I can. It's part of my nature.
I also carry a couple of spare battery packs for my cell phone, some stretchy velcro straps, a neck gaiter (can serve as an evaporative cooler and sun shield), extra riding gloves (full finger if it gets too cold), a rain poncho (tiny and disposable), a length of small nylon cord, and extra clothing as necessary to fit the weather.
Not looking at my trike and going by memory I may have overlooked some things, but it's a good start.
What are some things that come to your mind? Please add and share your comments.