Rolemaster- cus you can bleed out or die of shock- and lets not forget the Disintergation Crit Table and the ones for Hi Energy weapon platforms (gotta love the Spacemaster compatability).
Call of Cthulhu- because when it comes down to it, you're going to die or go mad-it's pretty inevitable.
GURPS- because no matter what how kick ass you get, a bullet between the eyes is still taking you out.
Chill- absolutely brutal attrition- great game, though.

Call of Cthulhu and Twilight 2000 were both designed to be gritty and deadly. However, experienced gamers will be quick to exploit flaws in the systems that will ensure survival. In Twilight it's possible to create a total bullet sponge that can live through anything but the rules are so convoluted why would anyone besides my friend Tim who enjoys the challenge bother with them? Call of Cthulhu makes it too easy to exploit the skill system to make a totally bada$$ combat monster, I've seen it happen.

Shadowrun is easy to die if you acted stupid. The system didn't, and now in Fourth Edition still doesn't, pull any punches. But at the same time it's easy to make a character that can shrug off anything thrown at them, especially Trolls. This flaw is fixed considerably in the new rules.

So my final vote as the deadliest game I have run or played is Call of Cthulhu d20. Using the d20 rules set it is not possible to exploit flaws in the system to make your character able to whip out an arsenal from under your duster and lay waste to the great cosmic evil. You can try but I can guarantee you won't be successful at low levels, I've seen it happen. d20 fixes the problems with the original rules and makes the game playable though still too deadly for my tastes.

Call of Cthulhu and Twilight 2000 were both designed to be gritty and deadly. However, experienced gamers will be quick to exploit flaws in the systems that will ensure survival. In Twilight it's possible to create a total bullet sponge that can live through anything but the rules are so convoluted why would anyone besides my friend Tim who enjoys the challenge bother with them?

Bullet-Sponge? I'd like to hear (read) a little more behind this.

I haven’t had the opportunity to play a detailed game yet, but everything that I’ve read points to The Riddle of Steel being a fairly deadly game. Any thoughts on this?

Bullet-Sponge? I'd like to hear (read) a little more behind this.

If a player were to pump up their endurance related score, I forget what it was called now, their health on their main body, where most attacks hit, can easily withstand several rounds from an assault rifle. Bullet sponge is what my friend, a long time fan of Twilight 2000 and Merc 2000, called this tactic.

The last game I played my wife made a big Samoan guy who could take all kinds of punishment and keep on trucking. The others in the party used to joke they could just use him as cover. Things like explosions and shrapnel that did damage to all body parts was a little more difficult to shrug off but it was still a flaw of the system. It's been so long since I ran Twilight 2000 that I can't remember exactly how she accomplished this and I'm too lazy to pull out the 2.0 book. :P

I didn't care for the unnecessary complexity of the system and scrapped my last game wondering why we didn't just play the same story with d20 Modern. So we did.

For board games it would have to be Aftermath.

For roleplaying toss up between Twilight 2000 or Paranoia, with Call of C rounding out the top three.

Did you hear that sound?

I like the hillarity ensuing from Og: The Unearthed Edition. There really are no advancement rules...just trying to live day to day in a prehistoric world with a vocabulary of half-a-dozen words is brutal, and fun! You have about a d6 worth of hit points, maybe hunting a wooly mammoth? Most lethal? Perhaps by realizing that the caveman ain't here no mo'.

Roll and keep- Legend of the five rings

Dream Pod 9's Silhouette system is harsh when you aren't in a Gear.

Roll and keep- Legend of the five rings

I'd have to agree with you there. You playing 3rd edition L5R I suppose?

Mechwarrior 3rd

The character creation charts couldn't kill your character outright, but they'd make your character wish he was dead.

Combat was lethal, both outside the mechs, and inside where a lucky shot from a rifle could breach the mech.

And the effort to roll up your character and stat him out could drive you to suicide.

Deadliest systems I played - taking only the rules into account, not the scenarios I'd say rolemaster (especially when the DM doesn't own the rulebooks but some of the players do - so they look up the criticals and the DM doesn't even have the chance to fudge...), shadowrun and Mechwarrior (I heard the latest edition of shadowrun is less deadly, but I haven't played, Mechwarrior is deadly in all editions I came to play)

I haven’t had the opportunity to play a detailed game yet, but everything that I’ve read points to The Riddle of Steel being a fairly deadly game. Any thoughts on this?

Ha! I made sure to read through all of the posts to see if someone brought this gem up. Most games talk about avoiding combat being a good decision, well this one means it. I love the damage tables.

Upward swing to the groin with cutting weapon

Level 5: "Weapon destroys pelvis and lodges just below the navel. Death is imminent."

Good stuff.

Kobolds Ate My Baby is pretty lethal. The DM can "win" by killing enough characters during a session, and can ensure that this happens by handing out points at will which force players to make a check to avoid having to roll on the Kobold Horrible Death Chart.

I'd have to agree with you there. You playing 3rd edition L5R I suppose?

Yep.

I heard the latest edition of shadowrun is less deadly...

Untrue. The new system actually evens out the lethality. Before most Trolls could shrug off anything but in Fourth Edition Trolls are still appropriately tough but can't shrug off bullets to the face they way they used to. I've found the lethality of Shadowrun was mostly up to the intelligence of the players. It was relatively easy to survive so long as you played it smart and didn't get in over your head, and, of course, wore armor.

I've been playing Shadowrun for years, across three of it's editions.

I would agree that Rolemaster could be brutual, especially on a single roll you could be screwed. Twilight 2000 I'd also agree to as being pretty rough.

The one I would also include would be Dark Conspiracy - which was also made by Games Workshop and used Twilight's system. I think what made it rough was that not only could you be killed by conventional means, but all the paranormal stuff that emerged could mess you up badly. It was like a nasty mix of Twilight and Call of Cthulu - to me at least.