I have a jolly useful little penknife which has a fully folding 1.7 in blade, couple of screwdrivers, small pair of scissors, bottle opener and can opener. Typical aircrew survival device. It normally lives on my keyring, except that every time I fly commercially I have to remember to put it in my hold luggage. Nearly forgot last time as the check-in lady and I were chatting about how she also used to fly in VC10s...then she asked the standard security questions and I remembered, apologised and popped it into my hold luggage....
But Lufthansa got the last laugh as my case spent the night in Frankfurt, whilst I spent the night in Friedrichshafen with only the clothes I was wearing!