Rationally speaking, we should all be counting in duodecimal. 10 can only be divided by 1, 2, 5 and 10 while 12 can be divided by 1, 2, 3, 4, 6 and 12. You'd of course pair this with metric units that are fractions and multiples of 12 to keep the nice round numbers. It'll never happen, of course, but it's one of those things that would make a lot of sense if you could wave a magic wand to make the whole world switch to it effortlessly over night.