As the title suggests.
What are your most funny, to vile in game sinful moments.
I have “forgotten” to heal over zealous DPS in dungeons in the past, and present.
Also. Before the fix and on my lock, long long ago, I would unleash Inferal and Doomguards in crossroads on the flight master without enslaving them.
I have summoned more people off of cliffs than I care to name.
I join highschool roleplays on moonguard then I’ll say “pass me assist I’ll help invite I know a lot of people!”
Then I remove everyone from the group 
Putting mage portals in AV to weed out the bad players too.
I love Alliance.
On my Warrior;
I had just gotten into a Blackrock Foundry Transmog run, open roll run, seemed good.
A boss goes down…the plate shoulders drop, the ones with the saw blades spinning inside them. Slag Shoulderplates.
I roll need because they look AMAZING and I won.
Another Warrior whispers me for the next 15 minutes;
“give me the shoulders”
No
“I deserve them, look at my achieves you’re nothing”
No
“I know the raid leader and I’ll have you kicked if you don’t hand them over”
I finally decided to just leave, and the guy still whispered me after I left;
“PLEASE just give me the shoulders”
I said okay, I will mail them to you in a few minutes, good enough?
“Awesome thanks”
I vendored those shoulders, and went to send him the few gold pieces I got for them, but he was on another server I couldn’t send gold to.
SOOOOO
I WENT TO his server, made a LEVEL 1, RAN TO IRONFORGE, and then panhandled the EXACT AMOUNT those shoulders vendored for, plus postage.
I even told the people giving me the gold what I was doing with it and why.
So I sent this mail to him, with the gold I pandhandled, and a word of advice;
To: (player name)
Subject: Unstable Slag Shoulderplates
“Don’t spend it all in one place ;)”
Fast Times at Moonguard High
After getting my Dungeon 2 set back in the day I went with unsuspecting PuG groups to UBRS and summoned the the boss for it in the Beasts room. I was then like, “Hey guys! Come check out this new boss!” Hilarity ensued.
There was this world boss in legion where you had to smack someone to wake them up from a sleep effect.
Well i was on my Warrior… rage starved… and hey free Execute proc from my legendary ring!
That poor little Gnome…
In MoP I had a hobby of perching on the Horde banners at their Shrine and dismount turtle shelling people as they flew past. Little tricky, needed patience, but they got some good air time before reaching the ground. I was really loose fingered with that shell.
shell works in Korraks… it’s nice to be able to use it again 
I like to spam anal jokes in trade chat.
Someone once offered me gold to “model” slutmog for them. Their slutmog. That they traded to me. I accepted, because why not get free money and slutmog?
It wasn’t even on Moon Guard.
I never actually watch boss fight videos. I say I do but I don’t actually do it. It’s pointless since I never learn anything from them. I do far better experiencing the actual fight hands-on.