We spotted an informative writeup over at AnandTech regarding various Xbox 360 Jasper identification strategies. What's a Jasper? Well, Jasper is the codename for the latest Xbox 360 models to roll off production and house tiny 65nm CPU and GPUs. The smallest, coolest, least power demanding, most stable and generally "best" Xbox 360 version to be manufactured.
Anyhoo, if you're in the market for a 360, we highly recommend you try to secure a Jasper 360 using a few of AnandTech's Jasper identification strategies. They've detailed tips including console lot number matching, looking up the console wattage and - most accurate of all - looking at the power connector. Remember, Jaspers are teh hawtness. You want Jaspers.