Human

There are mainly three types of humans in the Hellsing universe: normal humans, regenerators, and cyborgs.

While Hellsing's storyline seems to be naturally based on the existance of inhuman, unnatural creatures, humans still have an important role in this universe since most of the non-humans of Hellsing can remember being human at some point in time.

All the monsters of Hellsing's universe were human once. In addition, humans are not just defenseless victims of them; humans can defeat monsters, and are seen as the most valuable opponents for them, along with being the most wonderful and powerful beings of the world. As speaking of humans, we must make differences between normal human beings, regenerators (who are seen as humans by monsters but as monsters by humans) and cyborgs, whose identity is still human while existing in a mechanic body.

Standard Humans
Despite mostly having no supernatural powers in the Hellsing universe, not all humans are defenseless victims of vampires; humans can defeat them, if they are clever enough, and are therefore seen as the most worthy opponents of vampires such as Alucard. Some vampires also see humans as being fascinating and unpredictable, therefore seeing them as truly the most wonderful and powerful beings in the world.

Morals
In moral meaning, true humans are the strongest beings due to their will to fight against more powerful, inhuman creatures according to Alucard's moral codex (which is shared in some form by the Major and Integra). They fight "monsters" accepting the possibility that they can die; they don't enjoy fighting and massacring their enemies, but see it as a duty they must do. As Alucard describes it in Volume 3: "Giving up is what kills people. It's only when a person refuses to give up no matter what they earn the right of walking dowen humanity's noble pathway."

As for this description, not all people can be seen as true humans. The ones who only obey to orders and don't feel responsibility in connection with fighting monsters are called "dogs" by Alucard. In addition, even biologically inhuman beings can act like humans. This is true for Seras Victoria, who is still seen as a human by Alucard even if biologically the girl is a vampire (the quotation from him was said in connection with Seras). This goes along with Alucard's philosophy that inmortality is a gift that must be earned by living and fighting under the circumstances of being human. Alucard even accepts the regenerator Alexander Anderson as a human because of his bravery, while the priest was seen as a "monster" by his master, Integra in Volume 1.

We can even see an example for a monstrous being describing himself as a human. While the Major is undoubtly a cyborg, he still looks on himself as human as he has "a heart, will and soul". However, his humanity is debated by Integra since the Major seems to enjoy seeing destruction and massacre.

Power 

Statistically, humans are the strongest and most dominant race due to their numbers. Vampires, werewolves and other inhuman creatures are in minority, isolating themselves from humans for most of time in order to survive; if not, certain organizations solves the problems in connection with them, and hide the secret of unnatural beings from the public.

Biologically human beings in Hellsing Enrico Maxwell

Yumie Takagi

Pip Bernadotte

Renaldo

The Queen

The Pope

Heinkel Wolfe

Makube

Humans Respected By Alucard
Abraham Van Helsing

Sir Integra Fairbrook Windgates Hellsing

Walter C. Dornez(Before a Vampire)

Quincey Morris

Jack Seward

Arthur Holmwood

Alexander Anderson

Regenerators
Regenerators are humans powered up with bio-technology/nanotechnology. The only known regenerator throughout the series was Alexander Anderson; however, it is possible that after his death, Heinkel Wolfe replaced him as the trump card of Iscariot and was made to regenerator as well.

Enhanced healing
Regenerators are able to heal their wounds up to some extent. It seems like that Alexander Anderson's regenerative powers were equal to most of his vampiric enemies; however, he wasn't on pair with Alucard, and couldn't heal the part of his arm blown off by Alucard's gun developed against regenerators. However, the power of healing from even fatal wounds allows them to participate in dangerous situations; in Volume 1, Anderson was shot in the head by Alucard, but was able to recover himself and surprise the seemingly victorius vampire.

Another important fact about the healing of a regenerator is that they can't heal wounds inflicted before the process which by they gain the ability to regenerate from them. Anderson's and Heinkel's scars are clear examples for this. Oddly, this stands for their arch-rivals as well; Seras Victoria couldn't have healed her arm lost before he fully transformed into a true vampire.

Superhuman strength and speed

Regenerators seem to have strength and speed which is not normal for humans. For example, Anderson seemed to be able to hurt Alucard seriously with his bare hands during one of their fights; additionally, Anderson was agile enough to overrun vampires.

 Elongated life-span 

It seems like that a regenerator's lifetime is extended compared to other humans since they are aging slower (maybe due to their enhanced healing). For example, when Anderson was in his 70s in reality, he looked like a 40-year-old man. Heinkel, who may became a regenerator after the battle of London, hasn't aged at all even after 30 years.

Notable regenerators
Alexander Anderson (before becoming a monster of God using Helena's Nail)

Heinkel Wolfe (possibly becoming a regenerator after the battle of London)

Cyborgs
The only known cyborg throughout the series is the Major, the leader of the Last Battalion. While his body seems to be entirely mechanic (even his "brain" is admitted to be a chip by the Major), the nazi leader describes himself as a true human due to his will, emotions and power to fight and defeat Alucard. (Nevertheless, he lacks empathy towards other humans and enjoys the devastation of war. Because of this, his humanity is denied by Integra.)

The Major has no special powers like vampires or regenerators. However, his body's durability seems to be stronger than an average human body's since he survived a shot taken from a 88 mm anti-aircraft gun. At the same time, he died when Integra shot him in the head, which means even cyborgs have vital parts in their mechanic bodies.

Trivia

 * The Doctor looks and behaves like a human being, but it is unknown how does he not age. It is possible that he may be a cyborg as well.