Lumpy said:
That's why I think questline-essential NPCs should be unkillable.
We all know how well it worked out in Oblivion.
I believe that:
a) certain people should be hard to kill. NPCs like kings, warlords, generals, lords, etc should be well guarded and only an extremely well trained assassin or fighter should be able to get past the numerious elite guards. That in itself is an ultimate test of one's fighting skills and such battles should be as memorable as taking out one of them alien bases in XCOM.
b) decision to kill someone belongs (or should belong) to the player. The player should realize that killing a seemingly important character would most likely have some unforeseen, at the moment, consequences. If the player is ok with that or maybe hates an NPC with a rare passion (which would be "teh victary!" for me as the designer) and really wants to kill the fucker, then why should I say "No! Thou shalt not kill!"?