Probably the Aquatic Form druid quest from vanilla.
There was all sorts of things wrong with it. Having to travel across the entire game world, having to run through an area with mobs of far higher level than you with no stealth as well, how hard it was to find, and so on.
And all of this bumbling mess is what makes it so memorable and excellent.
The ability is not mandatory. You don’t have to run through Wetlands to get it straight away. It tries to teach you about how big the world is (and it’s BIG), it introduces its dangers and the progression system within it, and overall it just really makes you feel like a Druid - running around the wilds, being intimidated by them as you learn to master them.
Back in 2004 when I played that thing, I was so looking forward to a Cat Form quest.
It’s hard to pick a favorite from the thousands of quests in the game.
The Deaths of Chromie is technically a quest, that was a fun scenario.
For more lighthearted options there are the mail quest in legion Dalaran as well as the Murky quests/world quests. I love being able to embody his mantra in WoW (I murk, I die, I murk again).
In the more traditional sense, probably the Talador finale, though Godfrey killing Sylvanas is a close second.
Running through the Wetlands, dodging crocodiles and dying multiple times is surely a rite of passage for us OG players tho, right!!?
I still remember the little quest chain in Teldrassil where you help a satyr, get in trouble for it and redeem yourself by turning him into a frog.
Just hits all my nostalgia buttons as I started the game there and still love the music and vibes.
There have been some corkers in DF Ive loved too.
The belf who sacrificed himself in Azure Span for his friend and the Tuskaar who lost his pet made me cry.
Also loved the ‘evil’ drakthyr who ended up a babysitter in the Cobalt Assembly!
and of course…Taivan, the bestest of good boys ever!
Loved the way he was criticised for being useless at hunting and combat, but was an absolute legend as a rescue dog. Im usually a totally unemotional guy, but that quest chain really got me in the feels
My first true main character in WoW was an undead mage in WotLK. I really enjoyed leveling through the Forsaken zones and the development of the new plague, and after TBC gave them very little to do I was ecstatic when they picked that thread up again in Howling Fjord.
Finally getting the payoff to the new plague in a high production-value (for the time) quest chain with shocking moments and an amazing Undercity finale fighting with Thrall and Sylvanas was absolutely amazing.
There was really nothing at that level of excellence in WoW to that point and I don’t think similar chains such as BFA’s Undercity battle really came close.
I have never levelled a goblin all the way, but I think the goblin starting zone is the best in the game. All the quests are novel. Who can forget the rocket boots blasting the zombie pygmies.