Highly realistic medieval-ish, or is a fantasy setting alright? If a fantasy setting is alright, I'd recommend The Elder Scrolls V: Skyrim or Kingdoms of Amalur: Reckoning. Mainly anything that I can swing a sword and smash somebody in :P I would definitely recommend either of those, or if you REALLY want a game mainly for the combat, Dark Souls. You really feel as though you're swinging a heavy weapon when you use one in that game. It's not exactly sandbox though, so it might not interest you. (It has an "open world" in which all the areas are connected together amazingly, but it's not a go anywhere, do anything type of game. Mostly played for the good combat system) Of the two I mentioned before, if you want a heavy sandbox experience and have a semi-decent PC, Skyrim is a must of the two. If on console, either or is fine. But on PC, Skyrim with mods is better by far.