Physical: John is capable of defending himself and others in physical altercations, using standard military techniques combined with personal experience. Because he’s physically fit, it’s assumed that he has some strength in these situations, though he prefers to use his opponent’s movements against them rather than brute force. Specific fighting examples can be found in The Blind Banker, in which he fights against a masked assailant to save Sherlock's life, and a decent example of his trained style can be seen when he successfully topples Sherlock (a man a good head taller than him) and puts him into a headlock (ASiB).
He is adept at firing several types of guns and is considered to be a crack shot with a pistol. Despite being a building away, he managed to shoot a man through the heart even after the bullet had passed between two windows (ASiP). Even under the effects of a neurotoxin-induced fear, he doesn't miss a bounding, rabid dog on his first or second shots and successfully kills the beast when Detective Inspector Lestrade fails the task (HoB).
Mental: John is a trained medical doctor and army medic. It’s assumed that he has a professional grip on human anatomy, pharmacology, diagnosis, and medical treatment. He is suited for repairing wounds sustained in and out of combat situations or otherwise preserving life until in a more equipped facility. He has exhibited the ability to determine general time and cause of death in murder victims in numerous cases, including ASiP and TGG.
Emotional: Truly, an impressive amount of patience and tolerance is exuded by Doctor Watson, especially toward his flatmate. Everyone that knows Sherlock in the series has, at one point or another, expressed their amazement for John's ability to live with the detective and it's clear, to the viewer, that the drama of their living together is just the tip of the iceberg for what their colleagues know. Whether he's politely enduring the obvious flirting of the same sex for the sake of evidence (TBB) or staring down a man who is effectively telling him he's single-handedly put Sherlock at the mercy of his greatest enemy (TRF), John keeps his cool.
This also applies when John is put under stress. While we do see that John has expressed a genuine fear of dying (ASiP), he does not hesitate to put himself on the line for Sherlock when guns start firing or stand up to a kidnapper that has every possibility to kill him without leaving a trace (any episode and ASiP). John is courageous, then, and loyal. It is a popular trope by the series to suggest that his loyalty to Sherlock is what ends his relationships with his girlfriends (Blog and ASiB).
Weaknesses:
Physical: John is on the shorter side of average for a male, standing at about 5’7 (170cm). He is solid for his build, but he can still be overpowered. He is also a simple human, with no special powers or invulnerability to speak of.
His left shoulder has a large amount of scar tissue on it. He may become stiff there at times and it's probably a good place to hit if you want to knock him off his guard.
Mental: John is not technology savvy. (TBB, Blog)
He also does suffer from Post Traumatic Stress Syndrome. Previously, this manifested in a psychosomatic limp. However, as of late it has been compressed to nightmares (ASiP).
Emotional: Again, the issue of trust should be mentioned. John holds people at arm's length for the most part. He's sympathetic toward humanity as a whole, but he never shares about himself outside of tidbits in his blog. Even then, it's mostly in relation to his friend, Sherlock. A very good personal example would be that John never seems especially put out when his girlfriends leave him. In fact, at one point, he even confuses his current girlfriend with one of his exes. He makes no attempt to make amends and lets them go instead (ASiB, Blog). If he were serious about them, he could have done more; certainly his level of dedication to other activities shows he's capable of it.
His friends are a great emotional weakness for him. Not only does he prove that he'll put himself in life-threatening situations for Sherlock and Sherlock's cause (any episode), but he's also shows that he's allowing some of his morals to be bent by them. Sherlock has successfully convinced him to tolerate vandalism, to commit crimes such as trespassing, breaking and entering, burglary, and minor theft. Granted, all of these things are done in the pursuit of solving a crime, and that sometimes means working outside of the law, but these are almost certainly things that John would never do without a case and Sherlock's behest. When his landlady, Mrs. Hudson, is beaten and interrogated by American agents in A Scandal in Belgravia, his first concern is to see to her injuries. He clearly knows that leaving Sherlock in a room with one of those agents cannot be a good thing, but he leaves Sherlock to do whatever he sees fit.
John is still a soldier in ways that extend beyond his spartan personal space and his discipline. In the first episode, it is suggested that he misses the war as much as he is haunted by it ("When you walk with Sherlock Holmes, you see the battlefield." - Mycroft in ASiP). Indeed, John shows a level of excitement when the case is getting 'good' and they're closing in on their suspect. It is, in fact, the notion of chasing a suspect in the first episode that makes John forget about the limp everyone was telling him was psychosomatic. It has not returned in any further episodes.
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Physical:
John is capable of defending himself and others in physical altercations, using standard military techniques combined with personal experience. Because he’s physically fit, it’s assumed that he has some strength in these situations, though he prefers to use his opponent’s movements against them rather than brute force. Specific fighting examples can be found in The Blind Banker, in which he fights against a masked assailant to save Sherlock's life, and a decent example of his trained style can be seen when he successfully topples Sherlock (a man a good head taller than him) and puts him into a headlock (ASiB).
He is adept at firing several types of guns and is considered to be a crack shot with a pistol. Despite being a building away, he managed to shoot a man through the heart even after the bullet had passed between two windows (ASiP). Even under the effects of a neurotoxin-induced fear, he doesn't miss a bounding, rabid dog on his first or second shots and successfully kills the beast when Detective Inspector Lestrade fails the task (HoB).
Mental:
John is a trained medical doctor and army medic. It’s assumed that he has a professional grip on human anatomy, pharmacology, diagnosis, and medical treatment. He is suited for repairing wounds sustained in and out of combat situations or otherwise preserving life until in a more equipped facility. He has exhibited the ability to determine general time and cause of death in murder victims in numerous cases, including ASiP and TGG.
Emotional:
Truly, an impressive amount of patience and tolerance is exuded by Doctor Watson, especially toward his flatmate. Everyone that knows Sherlock in the series has, at one point or another, expressed their amazement for John's ability to live with the detective and it's clear, to the viewer, that the drama of their living together is just the tip of the iceberg for what their colleagues know. Whether he's politely enduring the obvious flirting of the same sex for the sake of evidence (TBB) or staring down a man who is effectively telling him he's single-handedly put Sherlock at the mercy of his greatest enemy (TRF), John keeps his cool.
This also applies when John is put under stress. While we do see that John has expressed a genuine fear of dying (ASiP), he does not hesitate to put himself on the line for Sherlock when guns start firing or stand up to a kidnapper that has every possibility to kill him without leaving a trace (any episode and ASiP). John is courageous, then, and loyal. It is a popular trope by the series to suggest that his loyalty to Sherlock is what ends his relationships with his girlfriends (Blog and ASiB).
Weaknesses:
Physical:
John is on the shorter side of average for a male, standing at about 5’7 (170cm). He is solid for his build, but he can still be overpowered. He is also a simple human, with no special powers or invulnerability to speak of.
His left shoulder has a large amount of scar tissue on it. He may become stiff there at times and it's probably a good place to hit if you want to knock him off his guard.
Mental:
John is not technology savvy. (TBB, Blog)
He also does suffer from Post Traumatic Stress Syndrome. Previously, this manifested in a psychosomatic limp. However, as of late it has been compressed to nightmares (ASiP).
Emotional:
Again, the issue of trust should be mentioned. John holds people at arm's length for the most part. He's sympathetic toward humanity as a whole, but he never shares about himself outside of tidbits in his blog. Even then, it's mostly in relation to his friend, Sherlock. A very good personal example would be that John never seems especially put out when his girlfriends leave him. In fact, at one point, he even confuses his current girlfriend with one of his exes. He makes no attempt to make amends and lets them go instead (ASiB, Blog). If he were serious about them, he could have done more; certainly his level of dedication to other activities shows he's capable of it.
His friends are a great emotional weakness for him. Not only does he prove that he'll put himself in life-threatening situations for Sherlock and Sherlock's cause (any episode), but he's also shows that he's allowing some of his morals to be bent by them. Sherlock has successfully convinced him to tolerate vandalism, to commit crimes such as trespassing, breaking and entering, burglary, and minor theft. Granted, all of these things are done in the pursuit of solving a crime, and that sometimes means working outside of the law, but these are almost certainly things that John would never do without a case and Sherlock's behest. When his landlady, Mrs. Hudson, is beaten and interrogated by American agents in A Scandal in Belgravia, his first concern is to see to her injuries. He clearly knows that leaving Sherlock in a room with one of those agents cannot be a good thing, but he leaves Sherlock to do whatever he sees fit.
John is still a soldier in ways that extend beyond his spartan personal space and his discipline. In the first episode, it is suggested that he misses the war as much as he is haunted by it ("When you walk with Sherlock Holmes, you see the battlefield." - Mycroft in ASiP). Indeed, John shows a level of excitement when the case is getting 'good' and they're closing in on their suspect. It is, in fact, the notion of chasing a suspect in the first episode that makes John forget about the limp everyone was telling him was psychosomatic. It has not returned in any further episodes.