LOTRO has PvP, but it is really Player vs. 'Monster'. You can play PvMP after your 'character' reaches level 40. Then you can start a 'monster' to play against other players that want to play on the "free people's" side. PvMP is available only in certain areas (Ettenmores).
That being said, LOTRO is now only $9.99 / month until the end of the year (or maybe Jan 30?) and if you pay in 3 month chunks, it will remain that price for as long as you remain active.
Guild wars, of course, is free of monthy fees. You must still buy the initial game and any expansions, though. It as real PvP, too.