I've noticed a bunch of misinformation in this video. (Which probably stems from the fact that you've clearly never played the game before prior to making this video.)
2:21 - The game-mode is not called Slayer. It's called Zombies. It's a user-made modified version of the Slayer game-mode. Slayer is the name of the games Deathmatch mode. The reason why they're holding a skull is because the skull is actually part of a entirely different game-mode called Oddball in which the players fight with each other over the skull while trying to hold onto it for as long as they can. The first person to hold onto it until it reaches the set time will win the game. However, while holding the skull, the only way to defend yourself is by hitting your enemies with said skull. This was perfect for the Zombie game-mode due to the fact that players couldn't just use a empty weapon and pick up ammo for it, which would break the entire game-modes structure.
3:26 - "Fun for the meme of it." Seriously? Need I say more???
4:39 - The game actually does not require you to have a copy of Halo PC installed. All you need is the CD key from your personal copy of Halo PC in order to unlock the installer and you're good to go.
Try to patch these quirks in your video up if possible. (The current YouTube editor is an absolute nightmare to use, so good luck with that!)
Other than that, it's nice to see someone new play the game. We hope that you'll stick around for years to come.