DM: As Torkon finishes his meal, the world goes hazy. He collapses to the floor. Torkon, take 5,000 points of poison damage.
Joe, player of Torkon: WHAT???
DM: Torkon ate cyanide. Enough to kill an elephant, in fact. It was in the pudding.
Joe: What are you talking about? I should have tasted it and stopped eating!
DM: Cyanide is tasteless, duh.
Joe: Torkons a dwarf, I should be resistant.
DM: Right, you get +5 to your saving throw to avoid taking 5,000 points of poison damage again next round.
Joe: This is stupid!
DM: No, its realistic. Cyanide is tasteless, and it kills you. Torkon ate cyanide, he didn't notice, and now he's dead.
Joe: There aren't any poisons in the DMG that do that much damage! You made that up just to kill Torkon!
DM: No, I didn't, and I take serious offense to your suggestion that I'm picking on you. The DMG doesn't have poisons that do that much damage because the DMG is based on wussy notions of "balance" and "fair play," instead of hardbitten realism. I play MANLY dungeons and dragons, and in my game, poison kills you.
Joe: This is stupid.
DM: Tough.