GerBarb
GerBarb was the first level 99 in Diablo 2's history, accomplished by a team playing hundreds of hours during the Diablo 2 classic days, before level 99 became an easily-achieved feat.
The full history of GerBarb and RussBarb (the 2nd place finisher in their epic duel to reach level 99) can be seen in the Diablo 2 section of this wiki.