Here is what I cart around to work, conferences, and travel.
Headphones
Bose QC15 Noise Canceling Headphones
The QC15's are the best active noise canceling headphones I have found. They are great on airplanes or at a noisy office. They work so well, I even where them when I'm sleeping on a plane without playing anything through them.
Bose MIE2i Headset
The MIE2i's are a pretty good value. They sound pretty good, are really comfortable and don't fall out.
iPhone Accessories
Apple Lighting Cables x 4
You can never have enough lightning cables if you are an iOS Developer.
Apple Lighting to HDMI
Great for presenting or playing Netflix on a hotel TV.
Apple Lighting to VGA
For when you have to present at a large company.
Apple 12w AC Charger
Apple 5w AC Charger x 2
Apple USB to Ethernet
mophie Juice Pack Powerstation Mini
Because iPhone batteries.
Storage
This Is Ground Cord Tacos (eBay Branded)
These are game changers. A co-worker ordered them for swag and I was hooked.
Topo Designs Dopp Kit
All of the above goes in this bag. It is a great size that fits nicely into a backpack, messenger bag or carry on.