Yes, I have~
But mostly, it was just for the purpose of messing around in boredom and having a joke with the people I usually battled. I remember 'sharking a shiny Caterpie, giving it moves like Megahorn and other such attacks~
And all the classic ones such as 'walk through the walls' on RS. You can discover some crazy crap whilst pissng about with those codes. Like, the 'sky' at the top of Sky Pillar. Its actually just puddle water, the same type found near Fortreee. Meaning you can walk around the sky, leaving little ripples of water behind you. Now THATS innovation in the field of laziness!
Oh, and of course, to obtain all the pokémon that can only be recieved via special events.
Or to get myself multiple TMs. I fail to see how doing stuff like that can be considered 'newbish'. I refuse to shell out for another GBA and another pokémon game, just so I can get the TMs I want. And I refuse to play through that damned Colloseum garbage again for them either.
OMG, I've used a Gameshark before! Guess that makes me evil, huh? =o
Really, I don't get why people are so uppity about this. Its not like people use codes to skip through the whole game or anything.