Popular fiction is full of scenes where combatants stealthily sneak up on a sentry and quickly disable them with a blow to the head, choke them or slit their throats so as to eliminate the sentry and slip past without alerting those beyond.
That can sure be a trick in Mutant Future where an average man can have 30 or so hp and a club does but 1-4 points of damage. In working on No Man's Land - The Mutant Front I've considered this sort of activity and worked out some guidelines.
Sneaking up on the sentry:
First one must actually sneak up on the sentry to take them out. MF has no explicit stealth rules but it does provide us with a couple alternatives for the task at hand.
Option 1. Use the surprise check: Use the standard rules for surprise with a slight modification on results as follows.
Attacker and Sentry Both Surprised: The sneaking attacker stumbles or kicks something alerting the sentry at about halfway in their approach to the sentry. They sentry may not certainly spot the attacker and they may be able to dive for cover and remain unnoticed (depending greatly on the situation at hand). The sentry will not raise an alarm unless the following situation warrants it.
Attacker Surprised: The sneaking attacker fouls up and is spotted by the sentry who may attack and will raise an alarm unless extremely unusual conditions still keep the PC from being spotted (illusions, invisibility, camouflage skin).
Sentry Surprised: The attacker is allowed to make the attack with no resistance from the sentry, see following guidelines for the types of attack
Neither surprised: The sentry will spot the character at an optimal distance. Roll for initiative whomever wins gets to act first. The attacker will be no more then 1/2 a move towards the sentry and no closer then 30'.
Option 2. Check vs AC. With this method one succeeds at a stealthy task by rolling dice vs their current AC score and getting that number or less. For characters with dexterity Modifiers to AC don't factor that into the AC score for this task but do apply that modifier to the die roll used.
Dice to be used in a stealthy approach of a sentry depend upon the discretion of the GM, the situation on hand and the players actions. As a rough guideline I recommend 1d12 for common tasks, up to 1d100 for extremely unlikely tasks.
ex: A Sentry is guarding a point on the perimeter of his forces encampment. The sentries position is carefully place but he is fatigued. The GM gives the player a d12 roll to approach in this situation. The would be attacks has a -1 modifier to Ac and a usual AC score of 4 but since the AC score doesn't factor in AC in this situation the AC is considered 5 and the player must roll 1D12-1 to get a score of 5 or less to sneak up on the sentry.
Knocking out A Sentry-
It easy in the movies, not so easy in real life and there are no rules for it in MF, so here is a suggested method.
On a surprised target the attacker makes his attack roll at +2 to hit. On a successful hit damage is rolled. The target must make a save vs stun or be stunned for 1-4 rounds and possibly knocked-out.
The following modifiers apply-
Target wearing helmet +4 to save
Damage score less then HD +2 to save
Damage score greater then HD -2 to save
Attacker using kosh/blackjack then -2 to save
If the save fails the target is stunned and has a % chance equal amount of damage suffered compared to current hp of being rendered unconscious.
Ex: Minko is armed with a blackjack and has snuck up on sentry with 28 hp who is wearing a helmet . The hit roll is successful and is for 3 pts of damage, the target gets a save at +4 for the helmet, the sentry has far more then 3 HD so the sentry gets an extra +2 to save, the attacker is armed with a blackjack so the save gets a -2 modifier for a total of +4 the save. The sentry fails his save. So we compare 3 to 25 hp (3 divided by 25 gives us 0.12) and we get 12%. The sentry is stunned for 1-4 rounds but the %roll comes up 43 and the sentry isn't knocked-out.
A sentry is knocked out for 2d10 rounds if the check to knockout is made.
Taking out the sentry by Choking
On a surprised target the attacker makes his attack roll at -2 to hit. On a successful hit damage the target must make a save vs paralysis for each of three rounds. If a save is successful the target is unharmed and breaks free. If 3 successive save fail the target is chocked out and rendered unconscious for 1d6 turns. A 4th save is required with a penalty equal to the number of turns the target would remain unconscious or they die from asphyxiation.
Targets that don't breath normally, can't be incapacitated by choking.
Taking a sentry out by slicing their throat
A surprised sentry may be dispatched by a careful and well executed blow which opens the arteries in their neck and kills them. An attack is made at -4 to hit and if the blow is successful the target is allowed a save vs stun or they suffer triple the normal damage roll and will continue to automatically suffer normal damage each round until death and are stunned for 1-3 rounds. Targets that save just suffer normal damage and are free to act,
modifiers to the save:
Target AC 3 or better +4
Target is large +8
Target has unusual anatomy +5
Damage roll is less then targets CON (or HD) score +2
Those nearby may notice the thrashing and activity while someone bleeds to death and flails about. If one survives the attack and bleeding during the stunned rounds they will be able to act (but will likely flee as they are bleeding to death).
Mutations and advanced medical devices may keep a target from bleeding to death. Creatures immune to stun checks generally can't have their throats sliced adequately enough to incapacitate them.
So, there we have 2 options for sneaking up on a sentry and 3 possible attack forms to neutralize the sentry. None of these options are meant to be used in standard surprise situations they are all intended for situations where the attacker has awareness of a relatively stationary target on guard. Each attacks type should be carefully considered before they are allowed in a campaign. Players may love them when they are sneaking up on foes, they will not care for them in the slightest if used against a PC guarding camp during the night.