As much as I'd love to see power armour, chainswords and boltguns become a reality, I don't want to be responsible for creating tech that'll help destroy the planet even faster.
So, I choose something constructive: Makers.
Maybe this kind of tech has appeared in other sci-fi media, I wouldn't know, I just know it from Transmetropolitan. It's basically a household appliance the size of a stove that creates... well, anything you need in everyday life. Food, drink, clothes etc - pretty much anything that's legal and not specifically trademarked, the maker will create it for you. All it needs is electricity and, of course, matter, be it in the form of high quality and density material or just recyclable garbage, to recombine at the atomic level into whatever pre-loaded configuration you choose.
Basically, instead of chucking most of your garbage in a bin, you can turn it into a delicious ham-n-eggs breakfast.