I'd have to go with PvE - Bards in Everquest at the Planes of Power expansion...
Which was the last I played the game.

Chant Kiting was absolutely sick, and you'd have a solo bard controlling a camp which would otherwise require 15+ players.
Just alternating songs/instruments between:
- running faster then the mobs could chase
- rotating which mob was charmed, which would have the swarm kill it for you with their insanely strong NPC dps... and breaking the charm just before the mob dies, switching to charming another mob
- doing a small aoe dot on all the mobs, to finish off those almost dead from the charm



For PvP...

Star Wars Galaxies, prior to opening the Jedi for anyone who wanted to be one....
I had a build which was, parts of Pistoleer, Fencer and Tera Kasi.

The dodge was sick, could basically go face to face with a dozen others and almost never get hit.
The accuracy was amazing, I'd consistently drop ten imperial scum working together with my single rebel hero.
And TK had a move, where you'd trip someone and they couldn't get up.

After a while, there was some kind of a patch.
And Rifleman/Another type of Sword user... became superior to Pistoleer/Fencer, but kept the same levels of TK in there.
It was strong, but not absurdly broken like my previous build.