2 Games I think do PvP perfectly for me:
Demon/Dark Souls
If you don't want to get invaded, don't run around as a human, but you lose out on the benefits that offers. Also, it gives a different set of advantages/disadvantages depending on if you're the one doing the ganking which is an interesting mechanic.
Conquer Online
You could attack anyone you wanted, however, if you are the one that struck the first blow, you'd be marked as a free kill for anyone else for a set amount of time and guards in towns would kill you if you tried to enter while in this "flashing target" mode. Also, if you actually killed the person you'd accrue a PvP point. Once you got enough of those you'd become a permanent target and could drop your gear when you'd die. Through your gameplay choices the game would cater itself more towards you. You want open PvP with gear dropping when you kill people? Keep on ganking. Don't want to PvP? Well tough shit its in the game, but at least you'll always have a chance to defend yourself and others will come to your aid against a free "open" target if you get attacked unprovoked.
Cutthroat league in Path of Exile is also great. Its basically Diablo 2 except everyone is permanently hostile.