Is it ok to start a list of interesting, but short mathematical papers, e.g. papers that are in the neighborhood of 1-3 pages? I like to read them here and there throughout the day to learn a new result.
For example, I recently read and liked On the Uniqueness of the Cyclic Group of Order n (Dieter Jungnickel, The American Mathematical Monthly Vol. 99, No. 6 (Jun. - Jul., 1992), pp. 545-547, jstor, doi: 10.2307/2324062).
Terence Tao's paper on uncertainty principle of cyclic groups of prime order. This was a prerequisite to understanding the motivating example behind this hugely influential paper on compressed sensing. I especially like the various historical references to Lemma 1.3 of the first paper, which shows how fundamental it is.