I've used completely underleveled teams against the E4 on multiple occasions. I've even posted my Emerald and HeartGold challenges (still need to post the HG Champion) to YouTube for anyone interested in seeing.
I was kidding in the title, but being annoyed by a word just because of the kind of people who use it is slightly childish to be honest.
Abusing defensive strategies in conjunction with x items can sometimes lead to pretty dramatic finishes.
PM me and I'll rate your team.
Azumarill's +1 Defense Curled 5th-turn Rollout completely crushing Glacia's Walrein in Emerald (complete with a critical hit!).
Of course, unless you have something with Shell/Battle Armor (like Armaldo and Drapion, among others), there's every chance you'll be screwed over by a critical hit bypassing all your X (Sp.) Defends and quite possibly demolishing your Pokemon, practically destroying every X item you put into it.
@Anser; Swag. :| Really now, you're being a bit childish with the constant whining about the word. There was no reason to insult the OP because YOU dislike the word, unless I missed the memo.
As for my own swag victory, my restarted Emerald, I used a Linoone all the way through the E4. Granted, he had a 10-level advantage over the Champion, but it was still a little tricky.
My FireRed main party included a Ratiacte, and she was a swag beast.
Signature is a WIP for the moment.
For now, I have claimed: Mewtwo, Member's Card, Wide Lens, Honey Gather, and Psystrike.