a modern day Assassin's Creed. the players would all try to assassinate each other by out smarting each other.
here's an example of how i see it playing out.
assassinations cost money. you gotta pay for the weapons don't you? can't keep using the same weapon weapon every time cause you'll get figured out. so you get a job. some fast food joint. on your way to work, somebody is watching you. hiding in the bushes or something. they watch you to see where you work, when you work, which way you go to work, etc... so one day while you're away, the person watching you plants a bomb in your car. this can trigger a mini-game for this person, where you have to match the right wires in a set time or the bomb doesn't work. you can get better bombs to increase effectiveness but that will also increase the complexity of the wiring. you get back to your car, start it and boom you're dead.
what you can do is create a bunch of default NPC's when the game is first started so that real people will fill the world as the NPC's get killed so that eventually the world is nothing but players. as for the RPG aspect....
successfully planting a bomb, successfully killing the target, aiding somebody in their own plan, gathering information about your target (via asking the other players if they know anything about the target) etc... will all give you experience as an assassin. then you can upgrade your techniques. like your bomb wiring, the more highly skilled you are means that you can wire better bombs as easily as you could with the lesser bombs. increasing your knifing techniques so you target specific areas of the body so that while you wait for your target to come around the corner, you tell your guy to run up behind him as he passes by via pressing buttons at the correct time and stab him in the neck for a swifter kill rather than being less skilled and only being able to burst out and randomly stab him. which would put you at risk to getting yourself killed.
for the items you can have your typical guns, knives, explosives, maybe even materials to build your own explosives. but you can also have different quality weapons. like a hand me down pistol from somebody else who has played a while and used that gun alot so it's worn and jams alot. or starting out as only being able to afford a butter knife. then stumbling upon some scissors so you can have a more gruesome kill (earning you even more experience for a more complex assassination).
i could keep going but this post is long enough
