Great question, this is something that I've been pondering for a little while now. I've been doing a fair bit of stage editing in the last few months and have been considering a 1510LFC pelican case not just for safe carry, but just as a "home" for all my mobile gear as well. I'm pretty sure it'll all fit.
What I currently tow along (in two backpacks) is my ...
I very rarely do this, but once very very early in my career I actually brought my entire studio to the other side of the country, lock stock and barrel (except the mixing console. Even I have my limits...), and built an ADR-studio in an apartment. That simply will not happen again though.
Nowadays, I see it like this (at least for now); if I really must do ...
Beyond the basics that everyone else seems to carry:
My own headphones
My own mouse/input device and any drivers needed
Backup of any drives
2 spare 32GB thumb drives
Small rolls of as many kinds of tape as I can remember to bring: Duct, gorilla, micropore, gaffer, spike...
Things to stave off hunger or boredom (food and eBooks)
I usually try ...
When I do theatrical design, I bring my mac, external sfx hard drive, mouse and matt, beyer 770s, and my minirator pro. That's the killer, because I can set up the PA to optimum standard before I playback my sound. Nothing worse then altering your audio, to find the rig has been garbling it up anyway.
And I shove it all in a pelicase.