I just wanted to add that the most superfluous and useless item in the entire game is the speck of dust… and I mean also in a literal way: the verb “use” doesn’t work on them.
The ratio “attention paid to it by players / usefulness of it” tends towards infinity. 
Since collecting specks of dust even appears in the to-do lists, I even hypothesized that they could have some hidden in-game purpose or usage, but I didn’t find any.