1) Not transfering to Area 52 for the AQ opening despite having completed the required quests - because I was afraid that it could upset my guildmates.
2) Disenchanting "Necro-Knight's Garb", one of the best looking robes ever, on my shadow priest with the launch of BC.
My absolute worst experience had to be in Cataclysm when I rolled a Rogue and used Ambush spam up until level 70, and realized just how terrible I was at the class. So I deleted the character because of how frustrating it was to learn the class from scratch.
Basically what it felt like:
"Oh damn, theres more than just Ambush and opening to a Rogue? Alright shouldn't be that hard, let me just go search it up..."
What are you talking about? While it is certainly not the the ability of choice on max level, because "lolz quadrupillion HP" it is probably the most fun way for me to play the class. Never did I have so much fun with a class as when you run around in the lower levels and your Ambush actually kills something like you actually are an Assassin or when using Aimed Shot like an actual sniper and the dmg scaling is so off that the shitty mmo combat system gets thrown out of the window. It's like headshots in shooters that actually take down enemies, well except when you are a tiger in farcry 3 and can take 5 sniper rifle shots to the face.
Meh anyway, taking up the position of raid/guild leader back in the day. It slowly eroded my sanity.
Making my first char an alliance in a PVE server. This during initial vanilla where the only way to change things was a reroll...
I was new to the game and had a bit of uncertain about going into an open PvP server.
Why oh god why!
Fixed that some years later when migrations and faction change alrdy existed.
Back when UBRS was a 15-man instance, my pug was in middle of the Rend Blackhand encounter when I got bored of healing and started going pew pew with my wand. Accidentally tab targeted and shot one of the npc spectators that spawn. The boss was almost dead when the entire instance came charging through the gate.
Kept my mouth shut the whole time people were trying to figure out what happened.
I was a couple of days into the game during my very first toon and got a quest from a dwarf in Stormwind to deliver a package to his friend in Loch Modan. Not knowing about the Deeprun Tram at this point, I ran from Elwynn Forest, through Redridge, through Burning Steppes, through Searing Gorge, through Badlands, and into Loch Modan at about level 9.
It took an entire night (I'm guessing around 10 hours) and I must have died at least two hundred times.
Then I met a Paladin who dueled me for a while and let me know about the train line from Stormwind to Ironforge.