I used to keep a few multi tools with bicycle specific bits in my bag, along with some tubeless plugs, tyre levers, UV led, and a full set of good quality hex L wrenches when I worked in a bike shop.
Some of them have transferred to my office job but the most useful things are a box cutter, a torch, and a mini ratchet with a comprehensive set of bits.
Oh and every jacket I own has a couple of USB sticks in, in case I need to save something offline or give someone a file off my phone or tablet.
Also ibuprofen. I always have some.