I probably carry too much but I’m paranoid…
All in a Dakine Nomad:
Tools
Mini Topeak Multitool (with Torx)
Park Chain Tool
Round plastic HTII tool
Spoke Key
Pump
Tyre Levers (Topeak Shuttle Levers)
Leatherman Wave
Spares
2 x Tubes
Patches
Tyre Boots
Quick Links
Few bits of chain
Chain ring bolts
Spare cleats and bolts
Random bolts
Chain Lube
Bit of Rag
Tape
Zipties
Other stuff
Blinky lights
Space Blanket
Emergency Clif Bar (always out of date)
Clothing to suit season/weather (generally at least a spare layer and a jacket if it’s not already raining.)
Asthma inhaler that i haven’t used for a decade.
Hayfever tablets in summer
Ibuprofen (unless i have robbed it and forgotten to replace it.)
I have also been known to carry a spare rear mech and rotor with me but that was not in the UK and in the middle of nowhere.