Best PvP encounters?
A) From the top of my hat... I recall my first Dwarven Battlerager who was into some good old fashioned drunken pugilist with an actual investment in the Taunt skill.

This was back in the days when pretty much every other non-magical melee character was a Rogue 4/Fighter 14/Weapon Master 7/Frenzied Berserker 5. Thus from level 1 to level 30, he would challenge every heavily armored tin can who brandished a weapon into a match of honest and fair fisticuffs!
I had a great laugh with the character in character and out of character. It was just plain fun to role play, and I did find it amusing how the most blood-thirsty individuals the Sword Coast had seen suddenly turned all timid once this dwarf of mine talked them into a corner they could not escape from. They just did not want to let go of their Falchions of Doom in order to trade blows with fists in a manly, honest, manner.
B) Oh, what about the time I actually rolled a Bard and talked in rhyme while sniffing some thyme, while also out insulting players that relied on a Shakespearean Insult Generators!
C) Oh, oh, what about the time I had a Spirit Shaman in the Flaming Fist and I cast Inferno on those animal companions some adventurers brought into the city without any regard to the setting. If only you knew all those times I just chuckled to myself watching a druid or ranger that brandished weapons being chased down by some burning bear or boar!

'
I do not think you should bring a beast into the city, it might knock over a brazier or two. *Nods-sagely.*'
The worst PvP encounters?
A) I guess because people cared for their mechanical advantages above all else, because I started to get complaints from DMs due to '
far too aggressive roleplay' because some were not '
comfortable with' along with complaint that I was not properly roleplaying a '
Dwarven Defender' and how I was bullying low epics with '
a level 30 character' that in reality was just around level 15...
B) Until I out insulted either a DM's bard or a DM's buddy's bard and was banned for it. I think it might have been on another server though.
C) Until the DMs decided to axe the Flaming Fist as a player faction due to general complaints and inactivity and forgot about my active character altogether. I think it was only some 3-6 months after the fact that a DM realised I was still playing one... Apparently I did not generate enough complaints the way I handled my character for them to even take notice, even though I kept posting IC reports on the guild sub forums and all that... Probably would still be playing as a member of the Flaming Fist had I not sent a tell to the faction DM in game.

*Sighs.*
I liked that Flaming Fist character of mine and kept trying to argue to bring the faction back, until my insistence on it transformed me into the avatar of all the wrongs the other Flaming Fist players had done or were imagined to have done. (
Burning animal companions is a perfectly appropriate in character action... 
)
There have been other guard factions since, and I've run into them once here and there. My biggest complaint is the way they handle their guard duty is inflexibility. The insistance on a binary choice between A or B, while there exists an entire alphabet of possibilities. It is also why I eventually gave up on resurrecting the Flaming Fist, and will argue against it these days.
Edit:
There is two sides to each coin. Third if you consider the edge.