I played vanilla for a damn long time, and their where some classes I simply could not defeat. I played a feral druid and hunter/warlocks where unkillable for me. The noobiest of nooblocks and huntards could eat me and I as a pretty decent cat druid. But the one ass kicking that come to mind was around 2yrs ago when i said fuck cats and rolled a DK. DKs where so OP in 3.0 I could easily take 2 or 3 (if lucky) of any other class.
Until I meet a disc priest. He must have been my level (72-73) and I was so certain with my anti-caster unholy build I could pawn anything with mana. I was very wrong. Very very wrong. And I was proved wrong over and over again over the next hour of priest camping. I remember running up to him and opening with Death Grip..