My favourite ones are for vacations... My wife and I will be taking our son (who will be 5 months old at the time) on his first trip that will require long haul flights (Australia - Vietnam - UK) so I'm currently working on a checklist for what to have in our hand luggage, and a separate one for the hold luggage. For me, it's part of the looking-forward aspect to such a trip, plus there are lots of things that we really don't want to forget, or run out of.
And anyone who's scuba dived will be familiar with the three item checklist that forms part of the pre-dive "buddy check".
* B A R (buoyancy, air, releases) in the UK
* A B C (air, buoyancy, clips) in the US and probably elsewhere
A potential life saver!