Keys from my local hardware stores always work. Maybe they spring for better machines, maybe it's just the operators spend more time and attention on them. But that's one thing I'll go there first for, no matter how many things I need from the big box store that the LHS doesn't stock.

It took me years to come up with a mnemonic to remember which pole of a battery to disconnect first from the charger. It's still a pretty lame one (pLus Loosens Last - best I could do), but I absolutely could not remember that without a mnemonic, no matter how many times I did it.