XBox 360 Memory Card 256MB
Not For Live!
This is perfect, if you're not on XBOX Live, as you can't fill it up with games. If you have Live get a Hard Drive - the majority of good things to download, require that you have one. Which is pretty lame but, downloads take up epic space on this card and would probably fry it!
Personally, I prefer a Hard Drive, but for people who can't afford it, this is the perfect choice