My version of Dogtrousers' disaster kit
In short ... Too much crap too
2xspare inner tube (why? because if you unexpectedly run into some thorns at speed on the road there's a good chance both wheels will suffer).
Tyre levers -try them out before you need them in the middle of nowhere. Lots of useless bendy plastic things about.
Puncture repair kit. Watch the rubber solution. Once you've opened it, you might find you've only got a tube full of air next time. It evaporates!
Dumbell spanner
6"adjustable spanner
TA socket tool (fits crank bolt)
Chain tool
Allen keys -some bolts are had to get at with a multi tool, so the separate allen key for those work better.
Small cyclists multi tool. Because I am a small cyclist? Maybe.
No 25 Torx key (for adjusting BB5 Disc brake)
Some spares ( nuts, bolts, allen bolts.)
Small roll Gorilla Tape
Cable ties
Power bank for recharging phone plus cable (Oh so smart phone has oh so tiny battery life)
Swiss Army Knife (I suppose that makes me a knife wielding thug)
Food ... whatever takes your fancy
Waterproof top
Spare layers (if necessary). I am usually too hot. A buff is useful, takes up little space and has many uses.
Lock
Pump (on bike) Full size frame pump.
Lights (on bike ... If necessary). I notice that some riders use flashing lights in daylight now. Your choice.
Phone
Wallet
Cash
Spare specs
Loads of tissues (kitchen roll for preference). Nose runs like a tap once I get hot and bothered, especially on cold days.
Bottle of water.
Plus random pointless stuff that has taken up residence in my bag. It's always in there, I don't add or subtract stuff dependent on the expected mileage (apart from food).