Close Combat
Distribution legal in ou:
Arcanine, Cobalion, Gallade, Granbull, Growlithe, Hariyama, Heracross, Hitmonchan, Hitmonlee, Hitmontop, Infernape, Keldeo, Lucario, Machamp, Machoke, Machop, Makuhita, Mankey, Meloetta, Monferno, Pinsir, Primeape, Sawk, Smeargle, Snubbull, Staraptor, Teddiursa, Terrakion, Ursaring, Virizion, Zangoose
All of these pokemon can make good use of Close Combat except Machop evolution line, Smeargle and Keldeo.
Also, all of them
use it commonly except Machop evolution line, Smeargle, Keldeo, Meloetta (I think) and Pinsir.
The main reason I didn't put it higher was because of the
viability of users.
The only ou viable users are Infernape, Lucario (Not sure about these 2), Staraptor, Mega Pinsir and Terrakion.
It
affects the game a lot, this is why it's good: Fighting type is a good type in ou hitting annoying pokemon such as Excadrill. Tyranitar, Bisharp and Chansey super effectively on their weaker physical side. It has a high base power with reasonable drawbacks. A drop in both defenses hardly matters because most users are frail anyway, going to switch out after using it or are sweeping your team. It is the best physical fighting type move in the game for anything (except machop line) that has access to it. It is also the main reason Mega Lucario was banned to ubers as without it, it would have to rely on a weaker special set with less coverage or rely on 75-80% accurate STAB moves (Iron tail and Cross Chop).
tl;dr: great move but not many viable users
EDIT: didn't know we weren't ranking them, removed rankings