OnlyKotoro

Seasons 1-3 Chapter 1.
After that they started nerfing double pump, which was completely legit strat.

For me it is definitely Black knight from Season 2 Battle Pass and The Reaper (OG John Wick) from Season 3 Battle Pass.
They look great since they are still from the times when Fortnite skins had their unique aesthetic.

What is your favourite Fortnite skin and why?

It should. The devs were hinting return of OG season some months ago. I have no idea when it will happen though.

I mean you can just play Solo if you don't want randoms yelling at you.

True. Fortnite 2017-2018 was the best. I left the game as Season 9 of Chapter 1 started. Since then I have only played during the OG season, which was pretty good, but very short.
Even skins were better during first seasons. They had this unique aesthetic to them, but as Epic has gotten contracts with companies like Marvel, the skins completely lost their uniqueness. Just 1:1 copies of superheroes or other famous characters. Meh.