If you're flying, take a passport or driving licence. Let's be honest, **** near all of you reading this have a passport. Take it with you. All this talk of trying your random other ID is just making the job of someone on a lower salary than most of us, that bit more crap.
Most of the people reading this will have flown in countries where it's mandatory to have proper ID in order to fly. We all know the score. Anything less than your passport or driving licence is just game playing. Just make everyone's life easier and stop pretending it's complicated.

The staffer who has a split second decision to make as the queue builds behind you doesn't need that sort of thing in their day. They well know they'll be shafted if something goes amiss. We can all make that ID check pain free and efficient, but we have to choose to be adults about it.