I know that Azurill already has a description - or at least a place on the ladder - but I'd like to do another for Azurill, this time nominating it for top tier.
Azurill - top
Availability - Right at the start, in floccessy ranch. You won't have to spend much time searching since it's got the second highest encounter rate there (I think, either Azurill or mareep - or both)
Stats Once it evolves into Azumarill it gets surprisingly bulky, with both of the defense stats quite a bit over 60 before you challenge Elesa. Attack stats shouldn't really be good, but huge power makes Azurill's attack stat high, just in time for Burgh!
Typing Well, it's thought largely round everywhere that water is the best type for in-game pokemon, and once Azurill is marill he is water type!
Move-pool & Major battles (They go 2 on 2 with Azumarill) For cheren's gym, you get Charm at level 11 which lets it take down Patrat easily and weaken Lillipup, despite poor offense at that stage, if you lower their attack by 2, and they're only boosting it by one, and since you have pretty good bulk you can survive lower hits. It's a stalling game, but it works great! It doesn't get much between cheren and Roxie but at level 23, a level lower than Burgh's highest, you get bounce (and before that slam) and they both take use of the huge power ability (when you catch one please make sure it has this ability without an attack hindrance in nature) but bounce, a flying attack, lets you get rid of Swadloon and Leavanny with ease and since he should have bubblebeam, he can probably get rid of dwebble, if not I let Psyduck take care of him. Now, I used Azurill once before, but I changed it for a magnemite for Roxie (I didn't know about bounce or anything like that) but in my mono-water run.. I only had water types to take down elesa, the electric gym leader, but I'd also replaced slam with strength at this point, and Azumarill learned Aqua ring (I also did a little domination of the battle subway, and get half way through train 4 (yes it was mix with my rival, and he basically supported with charm, but who cares, he had good enough bulk to survive!) is pretty good) and I got all my pokemon to level 32, 2 levels higher than Elesa's highest, 30. I knew that Azumarill would be the best pokemon here out of Psyduck, Ducklett (I traded for ducklett since my friend wanted a dewott I figured it ok) and Azumarill so I led with Psyduck. 2HKO and was outspeed, only managed an aqua tail on flaaffy that did next to nothing. Then, since I wasn't planning on using ducklett at all, I realized that he'll be able to outspeed one of them and land a surf (my friend was further through than I) and it got Flaaffy into red. Azumarill came in and swept all of her pokemon. Every one, after I'd set up an aqua ring (and she was holding leftovers) I only actually used 1 super potion on it and a paralyze heal, and yes, he did have strength. Anyway, Azumarill swept Clay with ease and that's as far as I've got, but looking at it's movepool I can relearn it roll out for Skyla and try a roll out sweep since she can't hit me super-effectively. It has ice punch via tutor for Drayden, and Skyla thinking about it, and he should sweep pretty well since Drayden nor Skyla can hit Azumarill super-effectively while Azumarill can. It has great move coverage for all gyms except for Marlon, its own type so you may have to let something else take care of him.
Misc. I repeat, make sure he has the huge power ability.