Not all Pokémon are made equal. Some Pokémon are used more than others, and even elite Pokémon players have their favourites.
Posted by Reddit user on r/Pokemon, here's a look at the most popular Pokemon used by top players on Pokémon Showdown. For those that don't know, Showdown is an online battle simulator used by Smogon, a hardcore Pokémon community. Showdown is popular because it provides an easy way to make a team without having to spend time capturing, training, and breeding Pokémon. You can just dictate a Pokémon's stats and moves, and get right into the nitty gritty of hardcore Pokémon against other diehard Pokémon fans.
Inside Showdown, there are different tiers, all of which refer partially to usage, and partially to power level. OU, for example, is "over used," and that's the major category in which most Showdown players compete. Other tiers include "ubers," which are Pokémon that are a bit too powerful to compete in OU, and UU, which stands for under-used. Beneath that is "rarely used" Pokémon, as well as "never used" Pokémon. Beyond that, there's the "anything goes" tier, where overpowered Pokémon like Rayquaza can roam.
With that in mind, here are the most popular Pokémon used by top players -- as in, the people with the most Showdown wins -- in their respective tiers: