While assassin Arya Stark may be downplaying her killing skills on Game of Thrones, she has already claimed her fair share of victims. And with the help of Gendry, Arya's new weapon on Game of Thrones will soon have her adding White Walkers to her kill list. No one can blame you if you were too distracted by the sexual tension between Arya and Gendry in the Season 8 premiere to really pay attention to the finer details of Arya's new weapon. But she has enlisted her former traveling companion/future lover to create a dragonglass weapon, so she should be collecting some undead for her bag of faces once the White Walkers come to Winterfell.
When Season 7 ended, Arya owned Needle and Littlefinger's Valyrian steel dagger. These are two fine weapons, but it's about time that super killer Arya was influential in the creation of an item in her arsenal. Needle will always be her signature sword, but with the army of the dead marching south, she's going to need something a little more practical to take on the White Walkers. And while Arya will certainly help slay some wights, she just may use her new dragonglass weapon to kill one of the leaders of this frozen zombie army.
Even though they are coming to kill all of humanity, the connection between the White Walkers and their wights is kind of fascinating. As Jon Snow and company have figured out, fire, Valyrian steel, and dragonglass all kill the zombie-like wights. White Walkers create the wights and if you kill a White Walker, all of the wights he had made die too. White Walkers are a bit tougher to kill since they are immune to fire (but maybe not dragon fire?), but they can be killed with Valyrian steel and, yep, dragonglass.
The Valyrian steel dagger is fine and good for close-range killings, like when Arya assassinated Littlefinger. But this dragonglass staff-like weapon will be far more convenient when being attacked by a horde of wights. And due to her training with the Faceless Men, we know Arya knows how to use a staff with deadly force. So with the addition of a seemingly detachable dragonglass spear, she'll be able to take out a group of wights.
Killing wights is all fine and good and utterly necessary, but it also feels like one of the most skilled killers around should take out a White Walker. The Night King knows and recognizes Jon Snow, but he and his fellow White Walkers may underestimate Arya and her nimble weapon. So if she's able to sneak up on a White Walker amidst all the chaos, she could best him like she bested Brienne when they sparred in Season 7.
As Arya displayed back then, she can fight a larger opponent using a larger weapon — especially when she has a secret and separate deadly dagger. And so she could use her sneaky Many-Faced God assassin skills and Syrio Forel water dancing training to fight a White Walker with her new staff before delivering a final blow with the detachable dragonglass spear.
The Last Harpy YouTube channel pointed out in its video about her new weapon that you can briefly see Arya spinning with a staff during a battle scene in the Season 8 trailer. And now armed with the knowledge about the new Gendry-made weapon, you can actually see Arya holding her dragonglass blade right at the beginning of the trailer. Presumably, upon receiving the spear, she holds it up and says, "I know Death. He's got many faces. I look forward to seeing this one."
Right now, the Hound, Brienne, Sansa, and Three-Eyed Raven Bran are the only people who really comprehend Arya's killer skills. And while it's unclear if she'll be putting White Walker faces in her satchel, the army of the dead (and Jon and Gendry) are going to find out just how deadly she is thanks to her new dragonglass weapon.