Shuttle makes small computers, but the X2700 is its smallest. The thermodynamically-unlikely dream of a true gaming box in such proportions remains elusive–it has but a humble Intel GMX 950 graphics chip–but at just an inch fatter than the Mac Mini, it's hard to complain.
At $400, it's pretty cheap, too, though it comes with Foresight Linux instead of XP. That gets you an Intel Atom 230 1.6GHz processor, 1GB of RAM, an 80 gig hard drive and a DVD player. You can double the RAM for $30 more, and add a 120GB drive for $20 (or up to 64GB of flash, if you're super-rich), but there's no option for Blu-Ray.
Does it have HDMI output? It does not, which puts it at an ease-of-use disadvantage against similar stuff from other makers (Brownlee just got Asus' miniature desktop model, and is loving it). Counterpoint: it looks cool and has 6 USB ports.
Product Page [Shuttle]