I found this today while browsing youtube, and watching it brought back some great memories. Give it a watch if you played WAR's RvR at some point, or if you wanted to see what it was like. For me, WAR made PvP enjoyable beyond what any other game before or since has offered. EA/Mythic had a great IP and a decent game to build upon, but they let it languish until most players (including myself) quit.
Reading their forums earlier today, I found out that due to exploits the RvR fortresses were removed at some point. That's pretty sad because the RvR fortress battles were a lot of fun. If you played oldschool WoW, think of the Southshore/Tarren Mill rivalries, but add a structure in between that a faction could capture for a short time. The controlling faction had access to special vendors, siege defenses (ballista, etc.) and a small army of high-level NPC guards. The opposing faction could then return with their own siege weapons (battering rams, etc.) later to assault the location. In addition, you could loot the enemies to gain a currency (like Honor points in WoW) and you could always pick up repeatable missions to kill X enemy players. Suffice to say it was grand.
So, when people figured out a way to exploit the system, the devs simply shut down the fortresses. Apparently it was too much hassle to actually set about fixing the best open-world PvP system they (and possibly any other game) ever had. The stupidity of this decision leaves me staggered.