The first pre-con I ever bought was the five-color one from I believe planeshift. I liked that deck when I was learning the game, but it didn't hold up when I actually started going to tournaments, and learned more about the game (such as the fact that you had a maximum hand size). The first deck I made myself was a massive five-color deck made up of probably around 100 cards (everyone else had their decks in card sleeves, which made me think that they too were running far more than the minimum 60).
I didn't get to play during invasion block, when there were cards in type II that encouraged five-color decks. I always thought that there may have been one during tempest block due to sliver queen, but I don't know that for a fact. I did have a friend who played a five-color deck, but all I know of that he had in it was Cromat and worship. I have no idea if he had ever run the thing in tournaments though.
Has there ever been a five-color deck that could be played outside of casuals? Obviously, I don't expect such a thing to be the top deck, I'm just asking if there ever was one that didn't suck because of it running too many colors?