The very first server i played was pRO or "Project" ro at the age of 8.
Of course i didn't understand it at that age and quit after 15 levels but a few years after i joined again and hopped from server-to-server.
The best time i had was in RebirthRO. Not because of the rates and ease of playing the server but because of the laid-back community and the one crazy guild that never failed to make me laugh out loud.