This subject is as clear as day to me, whilst there are many contenders there's one clear winner.
I used to really enjoy running random battleground's with a couple of friends, we'd start up a skype call and stick together, playing as an organised arena team against a set of random players. It's the only way to run battlegrounds and by comparison going in alone is not only boring it just seemed silly.
I would go into bg's alone from time to time and it was certainly gratifying to have those clutch moments, Aff locks used to get a lot of passive self healing through glyphs and talents (as well as haunt and drain life) so as an affliction lock it wasn't uncommon for me to do more damage than anyone else and die infrequently. Healthstones and soulstones certainly helped, there are few things funnier than dot dot fearing 2 or 3 players at the same time, slowly tapping at their health whilst they kill your ally and then grind you down, only to have them kill you and be at 25% health for you to resurrect via a soulstone once they turn around and you can finish them off.
Once had a similar moment in a 2's arena where they both killed my warrior pal and I managed to hold them off and win the match, was a great feeling for sure but sadly he quit playing shortly after.
Best thing I learned from going into bg's alone, make a macro saying that %t = healer. Whenever you're the only guy attacking him, hit the macro and suddenly your team mates will start attacking the right targets. Makes a huge difference.
My favourite bg was Arathi Basin. I loved it. I wasn't a fan of the similar Battle for Gilneas - the map is too small and it's too hard to cap flags. I wanted to like it but it never played out too well.
The guys I'd bg with were nothing if not entertaining, it wasn't uncommon for us all to be in fits of laughter the whole time and that's really what enjoying the game is all about.
I had one of those 3 seater mammoth mounts and I loved playing with a friend of mine (priest). We'd run straight to a base and he would aoe fear at the dismount, then start capping the flag. I'd follow the feared defenders and aoe fear them again as soon as the first wore off. by the time the second fear wore off my friend had pretty much capped the flag. Worked really really well, every time.
So anyway, most memorable pvp moment... I was in Arathi Basin with a couple of friends, together we were two rogues and a shaman. The shaman was busy defending somewhere when us two stealthies wandered over to the gold mine. It was defended by a warrior and a DK. great we thought, this'll be fun. My friend sapped the DK and opened on the Warrior. I waited by the DK, re-sapped him just before the previous sap wore off and opened on the Warrior. Before the 2nd sap on the DK wore off, the warrior was dead and we had both vanished. Watching the DK shit bricks knowing that he was next was great, he popped blood boil and death & decay trying to find us, knowing what was coming and we laughed together on skype. My friend asked:
"do you want to open on him and I'll distract the warrior when he rezzes from the graveyard?"
"no" I replied, "let's leave him there."
My friend and I laughed really hard and we both decided that if we just left the suspense of getting gibbed with the DK and the warrior when he returned it'd be much funnier. We made our way to the farm to find a bunch of reinforcements making their way to the gold mine (the warrior obviously called for help in bg chat) so we capped the farm without opposition then made our way over to the blacksmith.
I'm glad we left that DK alive, made for a much better story.