Though it is quite late to reply to this... here is the 'clear up' for .hack
If you are just looking for characters which where in Video Games, the following .hack// characters would be considered 'okay'
Project .hack
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All //IMOQ main characters and supporting characters, as well as 'minor' characters (Kite, Blackrose, Mistral, Elk, Helba, Lios, etc)
A full list of all characters can be found here:
http://dothack.wikia...Game_Characters
All //Sign cameo characters (they were in IMOQ as wandering AIs or memory fragments)... Tsukasa, Subaru, Mimiru, Crim, Bear, Sora, BT, A-20
.hack Conglomerate
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All //GU main characters, supporting, and minor characters (Haseo, Shino, Atoli, Kuhn, Ovan, etc)
Again, a list...
http://dothack.wikia...ames_Characters
Other .hack characters acceptable
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AI Harald
Aura
Jun Bansyoya (he had a character in R:1 and R:2 before his death, and was shown in the Terminal Disk)
Salvador Aihara (you can find his character in the japanese GU games, not sure about english)
Shugo and Rena (they were in //Fragment)
Also, due to the existance of //Fragment, you have to take into account some 'technical' factors here...
//Fragment allowed you to choose about 6 character models of each of the original 6 classes of the //IMOQ era, and recolor them in 5 colors (may be wrong on the number). So... technically speaking, all those would be acceptable as well.
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This was just an analysis of the question of '.hack' when it comes down to video game cosplay. Sorry if I over did it, it is just that I am a .hack buff.