Save or die spells really set apart RPGs for me. I find a lot of games generic and stale without them. I usally play melees (Rogues and Paladins). But having SoD (save or die) spells helps with character planing and counterspelling. It adds a lot of tactical spice to the game. A big bad should have death ward or a deathblock item on if the dev doesn't want an instant kill on it. As for disintegrate, spell manltes or item with a disintegrate absorption chance.
SoDs in D&D stop people from min/maxing as well. Maybe leaving your WIS at 8(-1) isn't such a good idea on your fighter/barb? Time take alittle off that maxed out STR, and think about your character.
I like to role play in my games. I find in D&D games playing a Paladin is awesome. I know that killing this NPC will get me lewtz and XP. But following the role and playing the part, will reward me with immersion! Helps bring me into this fantastic fantasy world. When playing Baldur's Gate, I keep a d20 with me. To see if my PC paladin notices my thief rummaging through peoples things. It makes it harder to play, but the story that happens out of Role Playing is awesome.
There needs to be some balance tho. Like a Paladin may not get all the goodies from going through peoples things or doing lawful acts. But once you get the Divine Avenger or any other divine relic, it really pays off.
