Ahh, the good old days! The MK community as we know it today started with MK Deception in 2004. I played that game way too much back then. When it was all said and done I had about 30,000 matches played online, and that does not include all the time I spent in Arcade mode, Practice mode, Konquest, and Chess Kombat (which incidentally, was awesome. I'd love to see it again in some form in MK10). We had a lot of good times on the MKO forums back in the day, there were clan wars and everything. Shout outs to the following players (I was on Xbox Live at the time so the vast majority of those would be from there, or people from PS2 that made the transition to Xbox) from back then:
B.N.R. - the best player on Xbox Live, hands down. This guy was in a league of his own and he eventually went on to join the most dominant clan on Xbox Live, The Outworld Gods. His Noob-Smoke was out of this world. I wonder what happened to him. Anybody know if he plays/played MK9?
Aldagod - another elite player. He came from PS2 and wreaked havoc on the Xbox community. Same question, does anybody know what happened with him? Is he still active in MK?
Alexei09 - that guy was ridiculously good with just about any character he picked. In the very beginning, before the arrival of BNR and Aldagod, he was the number #1 player on Xbox Live. Same question here, is he still active, perhaps under a different name?
Noobed - today we know him as
Noobe, a regular at MK and Injustice tournaments. I believe he also transitioned to Xbox Live from PS2. His best character was Noob-Smoke and he was another elite player that gave everybody a very good challenge. He also played a formidable Kabal.
AsmodeusMKO - an excellent Kenshi player and a master of the side-step. That guy side-stepped faster than anybody. I don't know how he did it, but before you knew it he would be right behind you and unleashing a combo on you. I don't know what happened to him either. Anybody know?
Champion Tiger - the undisputed best Jade player on Xbox Liver. This guy was a master of the partial combos. He would combo you to death with his beloved Jade and you never knew where he would interrupt his combos and start a new one. I was friends with him in the beginning and then we had a falling out for some reason. I've no idea what happened to him either. I believe he is from Mexico.
DJDreddy - oh boy, that guy was a riot. He had an amazing Baraka and playing with him was a blast. He would screech and yell on the mic, especially when he was losing. Lol. Good times. He eventually went on to lead the most dominant clan on Xbox Live called the The Outworld Gods. His English was terrible and he was known for making these long rambling posts that didn't really make sense to anybody, but it was lots of fun either way. Don't know if he kept playing MK or what?
ermacdoesexist - this guy was a pretty good Bo Rai Cho player (no Bo cheese either, of which I was very guilty. Lol). I don't really remember anything else about him.
RedSaleen - yet another good Bo Rai Cho player. He used Bo cheese sparingly. He was also very active on the MKO forums, he had a good understanding of the game's mechanics and gave good info about many characters. I am curious what happened to him too. Anybody know?
MKF30 (also known as
mkflegend) - boy oh boy, that guy was something else. He had a very good Dairou and then later Ermac, and eventually went on to lead one of the major clans on Xbox Live called the Chosen Warriors, of which yours truly was a member for some time in the later parts of my MKD "career" on Xbox Live. He was also known for his uncanny Scorpion imitation, both in voice and costume, as well as making extremely long, often nonsensical posts and getting into flame wars with just about the entire Xbox Live community. I went from friends to allies to arch nemesis with this guy, to eventually settling into an uneasy mutual respect sort of a state. Either way, much respect to him for being a great MK fan and a very good player. I believe he is still active on this forum.
MKF30 maybe?
KF Gaara - he was one of the early good Havik players (what a great character that was, btw. I'd love to see him make an appearance in MK10). We always had really good sets, but that's pretty much all I remember from him. Anybody know what happened to him?
KillerB - other than being a good Ermac player and feuding with this guy, I don't really remember anything else about him.
YouWillPerish - mostly known for his revolutionary Scorpion play, not much else is known about this player. I'll say this about him though, facing his Scorpion for the first time, early in the game's life, was a terrifying experience. He pioneered the Jab, Jab, Hell Fire/Sweep/2, 3, U+4 mix-up.
Smoke LK - a pretty decent Scorpion player and my teammate in the Dark Alliance, the first clan I was a member of. I was always friends with this guy throughout me entire MKD career.
Master Malone (also known as
IAmYourDeath) - this guy had the best Mileena early into the game's life. I was pretty good friends with him. I wonder if he is still active in the MK community.
GROY NYC (also known as
DomDizzle22) - the undisputed best Sub-Zero on Xbox Live, and also a formidable Liu Kang player. This guy was very tough to fight. You had to be at your absolute best and not make any mistakes if you hoped to have any chance of winning against him. I distinctly remember having a very tough set against him once that I barely won by one match and then I had a headache, no joke.
DoomsDayOfNY - a very good Noob-Smoke player. I believe he was a founder of a short lived clan called the Four Horsemen.
ThePunisher1 - that guy was an amazing Raiden player. That's all I remember.
Doohoo - I think he came into the game late in its life, but quickly improved and eventually became a really good player. At one point he went over to PS2 to face some of the best players there and came back an even stronger opponent.
BoobyBlaze - this guy was a character. Lol. He was known for having a great Scorpion and talking lots of trash on the MKO forums. He was also a member of my first clan, the Dark Alliance, then he quit and joined some other clan or some such. I remember there was a lot of drama involved during that incident. Much respect to him though.
FattMatt - man, I miss that guy. I was great friends with him, he was a blast to play against on Xbox Live. He was also the leader of the Dark Alliance clan after BobbyBlaze left. At one point I heard rumors that him and BobbyBlaze were the same person or some such. Wonder if he still plays MK.
FosterBrute - all I remember about him is that early in the game's life he had a great Shujinko. He played some Scorpion as well.
CRKFiend - the undisputed best Shujinko on Xbox Live. That guy was absurdly good. If you made one mistake against him he would start one of those endless Shujinko combos and that was pretty much the end of the round/match. Yea, scary. That's all I can say. I am sure if he still played MK he would be a major force not to be reckoned with.
easytobeat - do not be fooled by his name, this guy was anything but EASY to beat. He joined the community very late into the game, so late that I had pretty much retired by that time (late 2005) so I never got to play him, but I heard he became a beast of a player with many characters.
NJHitman - he had a really good Tanya, that's pretty much all I remember about him.
NinetyJ - probably the best Ashra player early in the game's life.
pighut - today we know him as @Pig of the Hut, one of the most skilled and most recognizable member of the MK community, but back then he started out as simply pighut. I believe he joined the MK community somewhere around the middle of the game's life, and if I remember correctly he played several characters, including Havik and Kabal.
Konqrr - the same
Konqrr we know today. I actually knew this guy even before the days of MKD. We faced off against each other in MK1 and MK2 online during the days of MAME/Kaillera so he probably is the MK community member I've known for the longest time. I even met up with him last year at EVO.
m2dave - the same @m2dave we know today. He was actually a PS2 player at the time so I never faced off against him, but from what I heard he had the best Dairou out there. Just as now, he was known back in those days for his amazing skill and knowledge of the game and his matter of fact, borderline curt posts. Lol.
So shout outs to all of those great players for the good times during the MKD era. If any of the names on that list are still active but under different name, do make yourselves known.
If I forgot someone, I apologize, and again, all of my experience with MKD was on Xbox Live so there are a lot of really good players from the PS2 side I never had the honor of playing against.
As long as MK is around so will I if I can 
I still remember you teleporting more then anyone with Raiden lol.
