Microsoft has just revealed that 343i's upcoming shooter, Halo 4, will require a minimum of 8GB of space for its multiplayer mode to work.
As the Xbox 360 4GB, Arcade and Core consoles do not come with a hard drive, Microsoft recommends that you pick one up.
Thankfully, your options are not limited to getting a hard drive, as the game will also run on an Xbox 360 flash drive, which come in 8gb and 16gb and provide enough room for your profile, game saves, and an installation of Halo 4.
That said, there's really no reason to go without a hard drive on the Xbox 360, because there's hardly any game these days that doesn't require at least a few gigs of space.
Halo 4 is set for release on November 6, 2012 and is exclusive to the Xbox 360.