The LA Auto Show's Design Challenge has a victor from among its Youthmobile 2030 entries: the Nissan Vehicle-to-Grid, aka V2G. It envisions a nationwide electric highway system (the "grid") driven on by Generation Z, and their cars will pay for use of the grid like a mobile phone plan. The V2G doesn't offer much in the way of variety, but it's ultra-efficient, cheap to run, and convoys of them can gather in interlocked formations called "flocks."
But when the Gen Z'ers get their hacking fingers on it, they customize it so it can be taken off-grid, creating the V2G Unlimited and the Halo-esque future we are beginning to think is inevitable. Sadly, none of the customized demos feature guns, which is all the V2G Unlimited appears to lack and will make it difficult to deal with the Covenant.
When the V2G is finished providing useful service, it can be recycled. Made of bioresin impregnated carbon nanotube cloth, a specially yet-to-be-created bacteria would devour the bioresin and leave only the cloth, which can be used to build another V2G. Or something. Check out the V2G in the high-res gallery below and start studying for the future, now.