Only MMORPG I ever enjoyed was Ultima Online (the old versions, not the newer dumbed down/more carebear versions). There's a player run shard called Defiance that has about 600-700 people online at max times.
It's a pretty good game IMO. The key points for me are:
Fighting over resources (no instances, all resources have to be competed for, but they regenerate over time as well).
PVP anywhere, any time (most towns have guards however, and if you commit a crime in front of an NPC you will get guard whacked and die instantly, or if you commit a crime against someone and they yell Guards)
There's a criminal system, everyone starts out "Blue" (innocent). If you commit a crime you are "Grey" (Criminal) for 2 minutes and 2 or 20 seconds, can't recall exactly) then you go back to being blue. If you are criminal anyone can attack you or loot your corpse without any penalties (other than you being able to aggress against them at any point until they die, even if they are blue. So if I'm a criminal and someone attacks me, I can hunt them down an hour later and if I guess they haven't died, we can both be blue and I can attack them). You can loot blue corpses but it's a criminal act (and timer is reset after each crime).
If you player kill enough innocent people you will become a player killer (Red) and will stay red for some time. I can't recall the whole system, but basically there's a short term count and long term count. If you only kill a couple people you'll be blue within a day or so. But if you rack the kills up over a long period continously, you'll be red for a long time. PK's are insta killed if they enter any guarded zones (there's towns that are not guarded however).
Almost everything on you is fully lootable (in this version Defiance runs, I believe everything is lootable on you). So it's a really big calculation of risk vs reward when you decide what to bring with you on adventures.
There's player run NPC vendors (players can set whatever price they want, but there's a pretty consistent going price for items, just have to figure it out). Or you can buy/sell some things from town vendors.
You can place houses in the world (kind of hard in some areas), and houses decay after a period of time (believe 14 days from the last time you visited the house). When a house decays the stuff falls on the ground and can be picked up by anyone who passes by.
You can steal from other players (requires quite a bit of dedication to make a thief).
