Sorting integers and the corresponding algorithms is one of the first basic topics one learns in computer science. Bubble-Sort, Insertion-Sort, Merge-Sort, Quick-Sort, Radix-Sort and even many more are discussed during the first classes. For a general purpose sorting algorithm, that is one that is based on comparison operations, it is known that one can not do better than $\mathcal{O}(n\log n)$.
Radix-Sort for example, which is not a general purpose algorithm, since it works only for integers, has a running time for $k$-digit integers of $\mathcal{O}(kn)$.
The sorting algorithm which i want to discuss today is Bead-Sort. It is based on a funny little idea to let gravity make the work for you. It has a theoretical runtime (assuming gravity is for free) of $\mathcal{O}(1)$. Implementing this on a normal pc would actually destroy this runtime because the gravity has to be programmed somehow.