I used this quite a bit myself and would like to see it continued, so.....I'll try and add on to it from here.
I'm mostly doing this for those who're on minimafia, but I'll add any names that're posted.

(Which means put the nickname you have for the list when you post V:)
Ones in parenthesis are IRC nicks that weren't included in the regular list.
Abs.— Absidoodle, Abbles, Absidongles, The Absmeistergeneral, The Doctor, Abby, Abscomeistergeneralcommandante, "Abs., M.D.", Distraction, Alien Spawn (most anything beginning with Abs)
Akonyl— Mr. Pennysworth, Ako, Ako-chan, Renako-chan, Jealkonyl, Akorn, Akonie, Ako-tan, Bee Princess Ako-chan, A-chan
aly_angelflight— Aly-mints, Aloe, Aly-chan, Aly the American, Alykins, Alylylyly, Anokata (Azurill-chan, Spinda)
angelranchan— arc
Azu— Azunyan, Azuzu, Mama Azu
Barakonda— Lil RoaRz
Beastly— Unavailable for comment
BK201— bk2
bluekaitou1412— Blue, Monsieur Blue, Bluechankun, bk, beekay, Ao-kun, Kai, babyblue, bluek, Paradox-kun
breva— brevvers
briggettkylie— bk3
Callid— Mars, Callie, Baka-Kaitou, Baka-Okiya, MarC, MarK, Callidus
Cheesus— Team Killer, K-19: The Widowmaker, Che Guevara, The Franchise, The Cheese, Cheesu, Cheesus van Cheese
Chelsea— Chellers, Chel-Chel, Chels
Cider— Cici (Sneasel, Thena)
cinnamoroll— Cinna, Cake
Citra Zaoldyeck— Citra, Citrus
Commi-Ninja— Commi, Commers, I-Think-I-Saw-Something-Move-Or-Maybe-It-Was-Just-My-Imagination, Comm-comm
Conia— That-Tree-That-Looked-Like-It-Just-Moved, The Conman, Connie, Conners, A-Random-Gin, Ginny, Edgey, Ganondork, Jerk, Conai, Conina, Stalker, Gin, ARG, Moms, Ginesme, Gunwale, Rival-chan, The Bush (Blackquill, LordN, N, NHarmonia, NaturalHarmoniaGropius, Darkwing-Duck, Chibi-N, Shi-Long-Lang)
Detective Tommy— DT, Tommers, Deeters
Dumytru— Dumy
Dus— Beerslayer, Raccoon, Drunk Raccoon, Otou-San, Kogorou
Edogawa4869— Edo-chan, Edo, Edo-bro, Edotoxin, Edo-kun, Jd-j, Edo-bro, Drama Boy (Disney-chan, RobinNewman)
Eve— Eevee, Evil
Excelsior— Excelsi
Fujiwara— Fuji, Fujimaybe, Fruitloops, Godot, Rum, Sambuca, Cofagrigus, Coffeegrigus
FuruyAkai— Furu, Furuya, Haku, Ichirou-kun, Ichi, Ichirou, Hachiroku, Hachikou, Kenmeri, Hakosuka, Pac-Man, Hachioji, Juzou, Hachi, 86
GinRei— GinRei, Rei-Z, GrumpyRei
Girl19— RJ, C-Chan
God— The Assassin
googleearth— Bash (bash7353, Yuusaku)
Grawwbear— Grawwblers, Graww, Rohoph, Her Grawwness, Grawwificus (Grass-chan)
hopelessidiot— Hayley, hopeless, Hope, Kangaroo Girl, Le-nee, Le-chan, Sid, Missus Hope, Hopey, Hayles, lessi, Kangaskhan, Kanga (Tequila, HaibaraAi, notGin, KangaskhanGirl)
Hoshi, tantei-chan— Hoshi
IdentityUnknown— IU, Idey, Ident, tonso, tonsostuff, pyre, Jeans, Atheleia
Jecka— Jex, Jeckorn, Jeckorneon, Jeckaitou, Jecksi, Jeckaoko (Korn, Chibi-Aoko, Akako, Castiel, Horsea, most anything starting with Jeck, Cheerios)
Jd-— Lucy, JNugget-, Batman, Hypeman, Jade, Captain America, DA BOSS, Boss-man, Jd
Juzagal— Juz, Juza
KainTheVampire— Kain, Kainers, KTV
Kaito Lady— KL
Kamite— Wolf (Houndoom, Chianti)
KawanoMino— Kiwi
Kirbypepe— Kirp, Kirbers, Kirpe, Curby, Kirbery, pepe, pink puffball
kkslider5552000— Slider, Scrappy
KleeneOnigri— Kleeners, KleeneTrollgiri, Kleeny, Kleene, Kleenigiri, Onikiya (GeneralTumbleweed)
Lyndsi— Lynx, Lynz, Lynzicus
mangaluva— Manga, Manga-chan, Chu, Chu-chan, Saylee
Meme— Memers, Memles, Memesy, memester
miakakiri— Miaka, Miaka-san, Mi-chan, Mi-kun (Manami)
miyano_shiho— Miyano, Shiho, Shehehe, JJ, Sherry, Shishio, Miyanou (Haibara, Chibi-Shiho, AppleJacks)
Mohorovicic— Moho, xXL, Mark, Moo-chan
monsi— monsers, monso, Takagi, Takagers, IRC Drama King
Moonlightmagician— mm
Nix— Nixxie (Chibi-Kir)
nomemory— nommers, nom, nommie, nome, nommy
Nyarl— Nyarlkins
Parkur— P, Pmeistergeneral, Chaosangel, Stalkur, P-chan, Par-kun, Snarky, Ms. Pennysworth, Parks, Kurz-chan, Parkurz, Parkles, Parkus, Curry, Vylash
PhoenixTears— Tears, PT, Feenie-chan, Ki-chan, PEE TEE, Firebird, Rival-chan, PAbsT-, Tearkins (Bourbon, Aura-Blackquill, Apollo-Justice, JugglerBourbon, Hydreigon, Ravio, Phantump, Apollo-Justice, Lord-Helix, Helix-Fossil, Klavier, Rotom, Bryrony, Haunter, Touya, Zekrom, Impa, Liepard)
pofa— God, pofs, pofers, the pofster, Keibu-han (Megure, Drifloon)
ProfParanoia— Prof, profa, pofa, Profi (noia)
queen misanagi— Misa-nee
Raiden— Rai, Shiny-Raiden, ShyRai, Raiders, RayRay, Raichu (Okiya, Chibi-Akai, Eisuke, Raijin, Zorua, Araide(n), Raikou, Trevenant, FrostedFlakes)
Raifuujin— KaitouRai, KaiRai, Raifuu, Fuu, RaiRai, Rai, Fuujin, GirlWithManyNicks, Nick Hoarder, Stranger, Kai
[spoiler=A lot of nicks for IRC]Registered:
KaitouRye
Rye
KaitouKage
HattoseiSora
KisekiReiko
Raiko
HattoRai
Kaitou-Kid
Kaitou1412
Zihi
MoonlightMagician
Kaito
Kuroba
Shinichi
Heiji
Saguru
Hakuba
Sera
Akai
Yukiko
Matsuda
Toichi
Chat-Noir
Chibi-Kaito
Chibi-KID
Chibi-Hakuba
Chibi-Shinichi
Chibi-Hattori
Chibi-Sera
Celebi
Zoroark
Braixen
Midna
ProfessorLayton
Descole
Clive
MaskedGentleman
Alfendi
Nemuri-no-Kaitou
Ventus
Gilbert
Tyki
Waka
Kurou
MaskDeMasque
PhantomR
Mephisto_Pheles
Luxray
JugglerKaito
Oki
TuxedoMask
Ghirahim
TheSpider
BillCipher
Unregistered:
Guest1412
Guest4869
MissingNo_
RedHerring
Mizuki_Seto
Katsuki_Doito
LuckyCharms[/spoiler]
ranger— Ringo (Sranger)
red.orchid— akai.ran, Orchid, Orchy
redangelran— rar
Reozen— Shiku, Reo
Sherlock3— Sherls
shinichi'sapprentice— SA (p10221, kokokrunch, akai, (keep a close eye on people who have all lowercase nicks in IRC with this one.... and typing all lowercase as well))
ShiraKiryuu— Shira
sonoci— Sonocers, Everybody's Child, Sono-chi, Sonic-chan, Kasonic-chan
Stopwatch— Stoppy, Stop (Chibi-Watch)
Suutashi- Suu, Suu-chan, Sushi, Suushers
Tanner-kun— Tanner, Tan, xcom, Battery Distribution Center Manager, Tan-tan
xpon— Ponx, Foxy, Ponxi, Pon, Pup, Vista-On, 7-On, Puppy
Yuri Iwamoto— Yuri, LadyDoctor, Yuri-chan, IwaYuri-chan (Vivillon)
Yurikochan— Yuriko, Trolliko, A-Random-Kidnapper, A-Random-Vermouth, Maya-Fey, Princess-Zelda, Princess-Souless, Yuri-chan, Vermy, OtherMoms, YuriTroll, Yurik, Yurk, Yuri, Kay-Faraday (Chibi-Ran, Chibi-Kay, Vermouth, RanMouri, Gosalyn, Malon, Pearl-Fey, Chibi-Maya, Princess-Scarlet, Princess-Kay, Klefki, Purrloin)
1412 Phenomenon: When rational people begin acting like mischievous phantom thieves/magicians
3DS FC: 1504 6005 4982
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/\ (O_^) Kaitou Approved