Typically, a "shiny kid", is a child between 8 and 16 who plays on public online game server (e.g. Minecraft servers). They usually "hack", or use cheat programs on the game and then moan to Admins when others do the same thing.
They enjoy making other players rage, by trolling them and attempting to simply annoy everyone in the game.
The term was originally made by an administrator on the TNT Factions Minecraft Server who goes by the name "Mlickism". In a text message to the Owner of the server ("Cydp3"), auto-correct edited his message to read:
"Damn fanboy shiny kids", as opposed to what he meant to say:
"Damn f**king whiny kids".
Please stop being a shiny kid and just play the game like everyone else.
The shiny kids were on last night. They were so annoying I just ragequit.
Admins can you please ban the shiny kids?