h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A good supermarket trolley (cart if you're American) would have:

1. A spring-loaded base that began near the top to make it easy to reach in and deposit purchases, then as the weight increased, moved downwards to make more room in the basket.

2. Front wheels that swivel 360 degrees, and back wheels that are fixed, like in the USA (so I'm told) - because it's then a LOT easier to push the thing around corners, and even just to go in a straight line. BUT see number 3!

3. A cunning handle located under the pushing bar that can be squeezed, in order to UNLOCK the rear wheels so that they swivel 360 degrees like the front ones. This would enable you to reverse out of sticky situations, e.g. while you are are selecting the best mushrooms, a vast crowd silently park their trolleys around you, boxing you in.

4. The best suggestion of all: Customers should be issued with a radio beacon, and each trolley would be programmed to follow a particular beacon around, without causing any jams or getting in the way of other people or trolleys. OK, sometimes you might have to wait a couple of minutes while your trolley caught up with you, but at least you wouldn't have to enter into stag-fights with rude old ladies who are determined NOT to exhibit the legendary good manners of the older generation... ahem.

A bit fanciful, but I'm being honest; right now, that's what I want.