I just beat the champion in my Ruby version, so to celebrate, here's a new topic. Post up your Champion-beating teams here, and let the world see their accomplishment.
They all started at about the same level when I first reached the E4, so you can tell who got the most use. An Armaldo with Ancientpower is always a terror, and can sweep Glacia's team with ease. If you raise it right of course (and it's one of my favourite Pokemon). It also handled about half of Steven's team (Aggron, Cradily, and Steven's own Armaldo) on its own!
Unlike Armaldo, I'd never gotten a Magneton to the Hoenn league before though and WOW, it's clear now why the player's guide lists it as a recommended Pokemon. Magneton with Thunderbolt absolutely tore through Phoebe's team, which the rest of my guys had trouble with, and it was able to handle Glacia for the first few attempts when Armaldo was too low-levelled. Magneton of course also happens to be pretty much specialized for Skarmory-killing, and since Steven led with one, his bird had no chance.
Tentacruel of course, had ice beam to deal with pretty much Drake's entire team, though he actually wasn't strong enough yet to one-shot Salamance. My own Salamance handled the revenge-killing instead, when Drake's knocked Tenta out. Speaking of Salamance, it was also instrumental in defeating not only Steven's Claydol, but his Metagross as well. When Steven sent out his final 'mon I still had five of my six left (only my Skarmory was knocked out), but Metagross proceeded to one-shot Magneton, Sceptile, and Tentacruel right away, with them inflicting very little damage before going down. Magneton wasn't able to get even one hit before being earthquaked.
Being down to my low-levelled (compared to Metagross and Armaldo) Salamance, and my powerful Armaldo, I decided to send in Salamance first to at least do a little more damage.
...And then a single flamethrower took Metagross, who was 7 levels higher (Salamance went up one from defeating him) from an almost-full health bar to nothing just like that. And so, I was pleased that I bothered to go through the trouble of catching and training a Bagon/Shelgon for 25 levels.