Eric Harris: Reb (obviously), Reverend, Indigo, WAR
Dylan Klebold: VoDKa (obviously), V, the god of sadness, death (well that's what Eric nicknames him in a online survey, IDK if Dylan would call himself that though or accepted it)
There was a foiled columbine copycat of a 14 or 15 year old boy who was arrested in i think 2004 or 2005, he had a journal in which he wrotes since E/D gave themselves nicknames, that he would do the same, he called himself "Micro". Why Micro? Idk, maybe its a reference to a micro smg, i really dont know.
This account got hacked.