yeah like Kargor said, there are few more possibilities how to PvP.
1) arena in Randol is only for training, but when do you get killed, you can lose part of yours exp/sp.
2) everywhere except inside towns, you can swith on PK mode and attack anybody, whos lvl 16+ - thats dangerous, you can obtain red or blue name, but you can get banned also if some social event is running and your opponent is just enjoying that event same time.
3) there are guildwars, the best opportunity for PvP, when members of one guild fight to another guild's members.
4) finaly if you are lvl 15+ and you are member of minimal lvl 4 guild, you can join a big Castle Siege battle, where owner guild of castle fight against another guilds - winner obtain nice bonus weapons and castle holds for mounth, when another one castle siege will come again
This is realy nasty and fun battle
)