One I apparently tried hard enough and managed to forget about.
So I used to have a kind of meh computer, when we raided ICC back in Wrath, and back then I'd just moved to Georgia, and back in with my parents to restart.
I knew their internet wasn't great (but didn't know that the wiring was very old and if it rained the internet was at best "unstable" - I was used to cable, after all - and thankfully that has now been replaced with fiber optic), but I did not realize how often DCs would happen when it rained.
One rainy Sunday evening, I spent an hour on the phone with tech support trying to get to my raid on time.
Half hour in, I manage to connect.. missing one of our DPS recording Deathwhisper's fight (which is now on Youtube - if you look up Powertrip Inc. (the name of our raid, inside joke of our guild) vs Deathwhisper, I'm the chick who came in at the end). They summoned me in as I was in flight, we made our way to Lootship. I ported up, and said over vent "I'm on my way!" thinking they'd already cleared trash, turned the corner to run down the corridor...
... and died a horrible death. The scenery loaded in when I did.
The raid group, dead, and the trash loaded in a few moments later as I floated elegantly above the carnage of our raid in spirit-form...
I didn't cause the wipe with my death. Everyone was too busy laughing to fight.
... I have not lived that down. To this day.