Aside from laptop and power supply.
I once had the wifi on my PC break (it started working again later for some reason) so ever since I always carry a USB wifi adapter.
I also keep a USB data stick and headphones. Also a mouse.
Everything I carry I carry because I realized I needed it once or twice and didn’t have it. So data stick, wifi adapter, mouse, headphones.
Why yes, yes I am boring.
Headphones, iPhone charger, several pens, notepad. Business cards.
I forgot, USB to micro-USB cable.
Does my tablet count? I never carry it unless on trips well away from home. I keep it in one of those red MediChoice socks that they give patients to walk around on slippery floors in hospitals, which is perfect. It has rubberized non-skid clogs on its, its made of anti-static fabric, and it’s bright red, easy to find. The only thing I keep in the sock with my tablet is a USB and a wall charger appropriate for whatever country I’m in. Extra USB and chargers for other countries in my luggage.
An outlet splitter, it’s the bomb for traveling. Lots of rooms don’t have lots of outlets and if you both have devices or more than one, it’s a real life saver.
I also always carry a two meter cord. So you don’t have to sit on top of the outlet if you’re out of juice.
Advil.
My laptop is used mainly for programming fire alarm systems. For this I need my programming hasp key and a USB to Serial adapter. I have four different DB9 plugs that work for most of my systems and a couple of telephone cables to connect to the various panels.
I also have a few flash drives, a mouse and a few hand tools.
For workday at my office: spare AC adapter, HDMI adapter, and micro-USB cable (so I can charge my phone off the laptop during meetings).
For business travel, I usually carry the work laptop, work phone, and personal Android tablet. My travel accessory kit includes: noise canceling earphones (Bose QuietComfort 20i), USB AC adapter (for charging my phone, tablet, earphones, etc), USB battery, MOGICS Donut (small power strip w/ international adapter and USB power), travel wifi router (in case hotel has wired ethernet but no or slow wifi - just replaced my old HooToo router with a new GLI model), retractable ethernet cable, and a small mouse.
Computer, AC adapter, CD drive, headphones, USB cord (white, to easily differentiate it from the other cords), surge suppressor, thumb drive, and headphone splitter. 8 items. And before moving my backpack, I always check to make sure all of this is with me.
A couple of memory sticks, spare pencils, a small packet of tissues.
And an eyeglasses repair kit which I started carrying when my glasses fell apart in the middle of Alaska. I got the last repair in the little store the train stopped at, and I suspect there wasn’t another for a bunch of miles.
Plus my business cards when I was working.
The laptop usually sits in the docking station and only goes in the bag, with spare charger, when I need to take it with me.
Otherwise, what’s always in the bag is:
Phones
Pens
couple of USB sticks
couple of muesli bars and salami sticks
Multi tool
wallet
neurofen
Portable charger
note pad
Same as above mostly plus one clean under short/under ware.
A decent pen, I hate those found in most hotel rooms
USB headphones for the laptop soft phone
Wall outlet/USB phone charger
Network cable with RJ-45 connectors. Something of a relic, but it’s still there.
Various paperwork
A cup.
Head office only has paper cups for coffee; I am in a regional office but I visit HO often enough to need a proper cup.
I’m a proposal manger, and my work location changes every 30-60 days (as I go from proposal to proposal). Usually the change is just to a different war room at HQ, but sometimes I go to a different office – or even a different state. I have a “rolling office” that contains:
[ul]
[li]USB keyboard[/li][li]USB mouse[/li][li]two monitor adapters (both VGA and DVI)[/li][li]ethernet adapter (just in case)[/li][li]power cord[/li][li]USB hub/replicator[/li][li]two pencil cases with various highlighters/Sharpies/labels/Post-Its[/li][li]a couple of thumb drives[/li][li]portable charger[/li][li]USB-powered fan[/li][/ul]
When I had a laptop, that would go in the rolling office, too. These days I have a Microsoft Surface, which I tend to just carry in my tote bag.
My passport and outlet adapters
My work-issued laptop spends most of its time in a docking station. I have a laptop for several reasons: meetings, troubleshooting in the lab, and most of all, for executing validation protocols. I carry my extra power adapter, cordless mouse, a few pens, my legal pad, ethernet cable, earbuds, power cord (for benchtop PCs that arrive without one), video adapter (some of our PCs have a weird digital video port that doesn’t work with the usual DVI output, so I need to use the old VGA cable, which works with the adapter). Sometimes a USB cable, sometimes papers, sometimes other odds & ends.