Has anyone ever heard of JTAGs for Xbox 360s? It's exploiting your Xbox 360 to be able to do a lot of things, some I won't mention due to a piracy rule.
You can:
Use custom dashboards
Use any sized hard drive
Mod games like COD in terrifyingly insane ways (like those mod menus)
Custom apps
Custom games (not indie games)
Console screenshots without a capture card
And a whole lot of other things.
It's not that easy though, as it requires a lot of mechanical knowledge and skill. Mainly soldering and lots of tools.
YOU WILL GET CONSOLE BANNED IF YOU GO ONLINE WITH IT, SO I RECOMMEND MAKING A SECONDARY XBOX LIVE ACCOUNT AND CONSOLE.Here's a guide, go read it.