All Out War. It seems plain and simple but it actually.....ok it is simple. It originated on the website Neopets.com when some roleplayer wanted to have a roleplay and just fight his damn ass off but nobody in the roleplay forums joined. The next day he went to the Evil things and monster sightings forums and posted it and it turned out to be a huge hit there instead.
Nobody remembers who created it or when it was made though, it's just always been there, like herpes. It probably isn't going on today still but if you find it is then join it, it's really cool. You can fight somebody, watch a fight, intervene in a fight, practice throwing virtual knives, that kinda thing, or just hang out or lurk.
dude: hey man, wanna roleplay?
man: no thanks dude, i'm meeting slayer on AOW.