Back on season 8 at the glorious 1400 bracket (pleasedontjudgeme), I played as resto/warrior and used Corroded Skeleton Key (for those who don't remember: http://www.wowpedia.org/Corroded_Skeleton_Key), we were playing against enhancement/hunter. When I let the hots go down, they hard switched on me, my warrior peeled while I ran to the pilar, really low HP, I took a silence shot and pressed the trinket key. When I hit the pilar I looked at my health: 1, the shield saved me big time.
That was definitely the most epic moment of my life on arena.
I also felt like a hero in the fight I got my 1750 achiev, that was on cata, season 11. I was playing jungle with a priest against a spiced chicken cleave (also with a priest). my hunter was CCed, I was putting pressure on the boomkin, I saw the priest positioning himself to heal the boomkin, I positioned myself so that when he started casting I focus kick him, start bursting, focus cyc, and he was dead. I was so fucking happy with 1750 rating and my challenger title I felt like I was the best player of the world.