Space programs in general. People living in space 24/7! Robots on the surface of other worlds! Yes, there are more exciting things in SF, but these things are cooler because they happen to be real.
Cryonics.
The word "iff". A very useful term meaning "if and only if", doomed to disuse because it would be pronounced the same as if. (merriam-webster.com even has the pronunciation as "if and only if"!)
Also, gender neutral pronouns and the rule that male pronouns CAN be used for gender neutral cases. Long since fallen from disuse, notably in English.
Weapons other than the AR-15 in tactical shooting events.
Cowboy action shooting events.
Red pandas. How adorable can one animal possibly be? Just do a Google Images search and try to say you don't want to hug one.
The clouded leopard is one big cat that definitely deserves more attention. Their fur markings are absolutely beautiful. They may not be endangered, but unfortunately they are listed as Vulnerable.
For that matter, the snow leopard. Top of the food chain in one of the most extreme environments on Earth: the Himalayas. And for that matter, all other leopards, from the common African leopard—it drags its food up into a tree so scavengers won't bother it!—to the critically endangered Amur leopard.
The mimic octopus is one cool cephalopod! First of all, its appearance is striking, with an amazing white-and-brown stripe pattern. Second, the "mimic" in its name is well-deserved. It can imitate many different animals, such as stingrays and sea snakes, to fool predators!
Speaking of sea creatures, let's not forget the sunflower star. This is a powerful juggernaut among starfish, a monster that can grow up to 1 meter in diameter and have up to 20 arms! It feasts on brittle stars, and you have to admit, it looks awesome watching large groups of the things all fleeing once a sunflower star shows up.
Station wagons, at least in the U.S. They combine the storage utility of crossover SUVs with the drivability of sedans.
