Say Blizzard announces a WoW 2, noting that nothing will carry over. Then, as a surprise homage, informs us we're allowed to bring our backpack with us.
You have 16 slots available to encapsulate your entire existence in Azeroth and beyond.
What do you bring with you, and why?
I'd go...
My mog set which can be trimmed to helm, shoulders, chest, gloves, belt, boots, artifact.
That's 7. 9 to go.
Then I'd bring my favorite Mounts (Invincible/S3 Netherdrake/Swift Spectral Tiger/Mimiron's Head/Ashes of A'lar) and my favorite pet (Spirit of Competition).
13. 3 to go. I've got a pit in my stomach thinking about this stupid hypothetical lol.
Then I'd take my first epic I ever got. A Glowing Brightwood Staff w/ a +22 Int enchant still on it. That thing was the best. I'll never forget how overjoyed I was to get it. That staff lasted me all the way through the late 50's and even through dungeons/ZG/Molten Core. I was wearing it on my first Ragnaros kill, and it even made a reappearance during Viscidus progression way later on! 14
Here's where I get highly frugal. Maybe too late, even. 15 would be my "still in wrapper" Golden Chest of the Elemental Triad. It was awarded for Challenge Mode Gold during MoP, and contains every piece to the Mage CM set. Don't ask why, but I kept it in the box and bought the mog from the vendor instead. Since it's one item, it counts.
Last spot. Now what? Another mount? Maybe something unobtainable to show my veteranship? Legendary items? There's so many of them.
I choose my Tabard of the Argent Dawn. 16. Another reminder of the halcyon era of my playtime, and what it represents is worth bringing to the new world.