With my current group I’ve run a classic ‘have a ship and do dodgy jobs’ Traveller campaign, a Game of Thrones inspired Burning Wheel game, an over-the-top Conquistadors in Space Rogue Trader campaign and some gutterpunk sword and sorcery.
In all of these games I’ve tried to be a ‘dice on the table,’ ‘actions have consequences,’ and ‘PC death is possible’ kind of GM. I’ve generally tried to impart a ‘life is cheap here’ vibe as part of the general flavor of the campaign milieus they move in. Moreover, since none of these games have had any known resurrection magic, my players have tended to be somewhat circumspect in their actions. Somewhat.
The thing is that while my players may do their best not to put their characters at unnecessary risk and are certainly not opposed to stabbing someone in the face as a solution, I find that life and death thematically structure my games in two ways:
1) No NPC wants to Die
Sure they may only be known as ‘the pirate with the oily beard,’ but none of my NPCs actually want to die. Even the Chaos Cultists. Provoking a straight-up fight is something they do reluctantly and usually only if negotiation or other means of achieving their goals have failed.
If outclassed, anyone with a modicum of intelligence will try to surrender, run away or, occasionally, beg for their lives. And if my players are playing hard bastards and murder fleeing or surrendered opponents, then…
Look, if the PCs are behaving like murderous scumbags, then NPCs are going to react accordingly.
Patrons will try not to be too closely associated with their bloody acts. Subordinates will disobey orders or mutiny if ordered into the breach once too often. Friends and relatives of their victims will look for vengeance. Their reputation will precede them (which can be a good thing if they are looking to intimidate them).
At best they will be looked at as disposable tools to be pointed at problems that can be solved messily. At worst they’ll be pariahs trying to escape the destiny their actions have brought upon them.
And that’s the thing about life and death in RPGs: How the PCs treat death has to have an impact on how their characters live their lives. Otherwise both are meaningless.