There’s a wight "instant kill" weapon that isn’t fire
Since Jon Snow saw his first wight brought into Castle Black in Season 1, we’ve been repeatedly told that fire stops the wight enchantment. Burn the bodies of the dead and they won’t become wights; burn the body of a "dead" wight and it won’t come back. Fire was the only way we officially were told to stop a wight, mostly because the show had four more seasons before the Army of the Dead needed to show up en masse at Hardhome. If the battle between the Night’s Watch and Army of the Dead at the Fist of the First Men hadn’t been whittled down to simply Sam running through some fog, we might have seen some more wight battles before Season 5, but hey, Game of Thrones knew it'd need some big bucks to spend on Season 7.
"Hardhome" introduced the idea that wights were more like zombies -- if you could crush the head or disassemble the body, you could immobilize the wight. This isn’t necessarily "killing" the wight; remember that poor Jojen Reed was stabbed to death by a wight skeleton that had been decapitated when Meera stabbed it through the head in Season 4's tenth episode, "The Children." Decapitating a wight does not stop it, you need to literally break apart it’s bones so none of it can be used offensively. One of the major reasons that the Army of the Dead is so intimidating is that -- at least up until this episode -- they appeared to only be stopped by fire.
Season 7 has been hinting this isn’t true, and very quietly confirmed it once Jon and his wight-capturing team make an unmentioned switch to dragonglass weapons. When Sam is reading about the "mountain of dragonglass" underneath Dragonstone, he’s looking for ways to stop the White Walkers, but when Jon shows up to make his plea to mine the dragonglass, it sounds like he needs enough of it to take on an entire army. That’s because in the world of Game of Thrones, we know now dragonglass affects wights like an actual weapon attack would on a flesh-and-blood, mortal enemy.
"Beyond the Wall" doesn't overtly recognize this transition, but right before Jon and company get saved by Daenerys, we see The Hound, Jorah, and Tormund all switch to dragonglass weapons. Beric has his flaming sword, and Jon has his Valyrian steel sword. All three of those weapon types look like they fell wights, where as before we had to depend on something like Benjen’s fire chain. The things that can kill wights has expanded from "anything on fire" to "anything involving fire, dragonglass, and Valyrian steel."
The show hasn’t gone far enough to explicitly make this connection, but knowing that next week we’ll likely see Cersei presented with a wight, that would be the place to hammer home the importance of dragonglass versus other methods of killing wights (so we don’t have to cover it in Season 8).