Power Armor:Enhanced Strength: +20 to Strength after you account for Unnatural Strength.
Auto-senses: +10 to Awareness tests for sight and sound (stacks with implants for a total of +20). Sees in total darkness and never takes penalty for insufficient light. Immune to stun or flash grenades.
Osmotic Gill: As long as armor is intact (has suffered less damage than there are armor points), is powered and the helmet is on, the armor is a sealed environment.
Bio-monitor and Injectors: +10 to resist poisoning and weapons with the Toxic Quality (stacks with armor for a total of +30). Ignore the effects of Critical Damage for 1d10 rounds (6 doses). Negates Stun after 1 round.
Vox Link: Acts as audio/visual transmission. Can see through another Battle-Brother's eyes and view vitals.
Magnetized Boots: Equivalent of Magboots in Wargear section.
Nutrient Recycling: For every two weeks with no food, make a Toughness test or suffer one level of Fatigue. Difficulty increases by one step (-10) for each additional two weeks.
Recoil Suppression: Negates the -20 penalty for firing basic weapons (like Bolters)
Heavily Armored: -30 to Concealment and Silent Move.
Poor Manual Dexterity: -10 for using non-Astartes weapons. Takes at least 5 min (and normally 20 min) to remove armor.
Implants: (Not every Chapter has all the implants)No Bleeding: No additional damage from bleeding (p. 260) except that caused by Warp Weapons.
1/2 Critical Damage (Larraman's Organ): When suffering Critical Damage, half the total rounding up.
They Shall Know No Fear: -10 to Willpower per level of Fear in solo Mode. In Squad mode, Leader takes Willpower test (with above penalty) or suffer one point of Cohesion damage for every Fear level. (p277)
No Need to Sleep (Catalespian Node): Marine suffers no penalty for not sleeping for long times.
Resistant to Poison: Premnor grants +20 to resist ingested poison (stacks with armor for a total of +30), Oolotic Kidnet grants a reroll to resist poisons including weapons with the Toxic quality.
Multi Lung: re-roll tests for suffocating or drowning, +30 to resist gasses and a reroll. Can breath water.
Detect Posion (Neuroglottis): Detect poison with a Challenging (+0) Awareness test.
Tracking (Neuroglottis): +10 to Tracking tests against a target he has tasted.
Spits Acid (Betcher's Gland): Can spit poison (Range 3m; Damage 1d5; Pen:4; Toxic). With three or more degrees of success, can blind enemy. Can chew through metal or non-living substance slowly.
Resistant to Heat and Cold (Mucranoid): Rerolls all Toughness tests caused by extreme temperatures.
Omophagea: Can gain knowledge or skills from eating flesh.
Honor the Chapter (Progenoids): Must pass Willpower test to leave a fallen Battle-Brother behind without removing Progenoid glands.
Heightened Senses (Occulobe and Lyman's Ear): +10 to all tests using hearing and sight. (stacks with armor bonus for a total of +20)
Suspended Animation (Sus-an Membrane): Can enter a state of suspended animation by will with meditating for 1d5 rounds or when knocked unconscious. Hard (-20) Medacae test to revive
Melachromic Organ: Resistant to radiation at GM discretion. See also: Salamander's Chapter.
No Bonus for Size (Black Carapace): No bonus to hit due to Hulking size.
Starting Traits:Ambidexterous: No off hand penalty, can still be right or left-handed for fluff
Proficient with All Weapons: Only exception is Exotic type weapons like Sniper rifles and Conversion Beamers which test at -20 or not at all at GM discretion.
Bulging Biceps: No need to brace to fire heavy weapons at semi or full-auto.
Dark sight (granted by armor):
Suffer Not the Alien to Live (Deathwatch Training): Automatically confirms Righteous Fury on Xenos (no need to reroll attack to confirm critical damage when you roll on a natural 10 on damage to gain 1d5 Critical Damage)
Killing Strike: When using an All Out Attack, player may spend a Fate Point to make attack impossible to parry or dodge.
Nerves of Steel: May reroll Willpower tests to avoid or recover from Pinning.
Quick Draw: May ready a basic, pistol or melee weapon as a Free Action.
Resistance Psychic Powers: +10 to resist psychic powers.
Unarmed Master: Unarmed attacks do 1d10+Str in Impact damage and are not Primitive.
Unnatural Toughness and Strength: Doubles Characteristic bonus before applying other bonus.
Hulking Size: Agility bonus +1 is movement in meters.
Conclusion:Astartes are very difficult to poison, very hard to take out and almost impossible to kill. Even outside of their armor, they are formidable. As hard as they are to kill, I can't conceive of someone being able to subdue and capture. Even if they were able to, there is no way to hold an Astartes indefinitely.
This list was necessary because Astartes break almost every basic rule that mortals have to follow and those exceptions are very often not accounted for int eh rules. I understand this because the rule book is for the GM to run human and non-human enemies as well as the players to run Space Marines. It is frustrating when you do not have a perfect grasp on the rules and are applying penalties or not stacking bonuses like you should be because the rules section does not mention the Astartes exception in the rules section. Often the exception is in completely different sections of the book like Wargear or character creation.