This question is (inspired by)/(shamefully stolen from) a similar question at MathOverflow, but I expect the answers here will be quite different. 

We all have favorite papers in our own respective areas of theory. Every once in a while, one finds a paper so astounding (e.g., important, compelling, deceptively simple, etc.) that one wants to share it with everyone. So list these papers here! They don't have to be from theoretical computer science -- anything that you think might appeal to the community is a fine answer.

You can give as many answers as you want; please put one paper per answer! Also, notice this is community wiki, so vote on everything you like!

(Note there has been a previous question about papers in recursion-theoretic complexity but that is quite specialized.)

The 1936 paper that arguably started computer science itself:


Alan Turing, "On Computable Numbers, with an Application to the Entscheidungsproblem", Proceedings of the London Mathematical Society s2-42, 230–265, 1937. doi: 10.1112/plms/s2-42.1.230


In just 36 pages, Turing formulates (but does not name) the Turing Machine, recasts Gödel's famous First Incompleteness Theorem in terms of computation, describes the concept of universality, and in the appendix shows that computability by Turing machines is equivalent to computability by $\lambda$-definable functions (as studied by Church and Kleene).
