This pisses me off so bad:

Quicksort does NOT have "the best big-O". It's big-O time complexity is O(n^2). Big-O refers to the worst case time complexity. Quicksort will on average take (n log n) time complexity, but that's not its big-O, that's its big-Theta. Some try to skirt this by saying "if you randomize the order of the data first, it will be sorted in big-O of n log n" but again, that's the average time complexity, not the pathological case.

A lot of CS books teach this wrong. Please stop being wrong: O(Quicksort) is O(n^2)