Warning!! The following contains spoilers for Marvel's Guardians of the Galaxy, available now.
In Marvel's Guardians of the Galaxy, the team is former space pirates and criminals turned heroes-for-hire who try to live up to their name. Unfortunately, their less than scrupulous intentions tend to bring them into conflict with those tasked with protecting the vast universe as a whole.
The Nova Corps is one such organization tasked with protecting the entire Andromeda Galaxy and much of the Milky Way Galaxy, including Earth. The Corps' members are all to some degree imbued with powers called the Nova Force, which comes from a planet-wide supercomputer called the Xandarian Worldmind. Whether it's against petty criminals, pirates and vigilantes, or god-like beings bent on total annihilation, these are the Nova Corps members that have fought for the galaxy, as well as their Marvel Comics counterparts.
Samaya
A senior member of the Nova Corps, Samaya held the rank of Denarian and led a squadron into battle against the Chitauri invaders when they attacked Xandar in the Great War. During the battle, she performed a suicidal attack on the Chitauri's Leviathans to buy time for people on the planet to evacuate. She was posthumously awarded the Medal of Valor and given a memorial on New Xandar.
Samaya remains very similar in the comics in which she dies defending Xandar, except that it's during the Annihilation War and not at the hands of the Chitauri. It's also possible that her comic version held romantic feelings for Nova Corps leader Richard Rider before dying.
Ko-Rel
Ko-Rel was once a member of the Kree Imperial Army and fought on the side of the Resistance against Thanos and his Chitauri army in the Galactic War. She was also a former lover to Star-Lord, with whom she now has a complicated relationship. Afterward, she joined the Nova Corps and eventually rose to the rank of Centurion and captaining her own ship, the Hala's Hope. She played a role in creating a quarantine zone for dangerous technology and weapons used during the war.
While there are obviously some major differences from her comic book counterpart, Ko-Rel was still originally a soldier of the Kree Empire. However, rather than the Galactic War, she fought in the Annihilation War and played a key role in saving Richard Rider. She also perished at the hands of Gamora in the comics.
Malik Tarcel
A Centurion and member of the ruling council, Malik Tarcel was also an accomplished diplomat that represented the Nova Corps to the Shi'ar Empire. During the Galactic War, Tarcel was able to broker an alliance with the Shi'ar. Unfortunately, this was short-lived after an agent of Thanos attempted to kill both Tarcel and the Shi'ar ruler. Tarcel didn't survive the encounter, and the Shi'ar rejected the alliance shortly afterward. A memorial for Tarcel was erected on New Xandar in honor of his sacrifice.
Tarcel's comic book counterpart was recruited after the events of Annihilation and would later be made the new Nova Prime following Richard Rider's expulsion. He would take part in the War of Kings in which he was captured, tortured but later rescued by Garthan Saal, though he hasn't been seen since.
Rhomann Dey
Rhomann Dey was the original leader of the entire Nova Corps and held the rank of Prime Commandant, seeing to the day-to-day running of the organization. During the war, Dey led a large portion of Nova to battle the invading Chitauri to buy time for the evacuation of Xandar. He would later be listed as missing in action and presumed dead, with a memorial erected to honor him.
Dey's comic book counterpart remains mostly the same except that Xandar was instead invaded and destroyed by the pirate warlord Zorr. He would later flee to Earth and make Richard Rider the new Nova Prime in a desperate attempt to keep the Corps and, by extension, the galaxy from falling.
Nicholette Gold
In the Guardians video game, Nicholette "Nikki" Gold is a Nova Corps Cadet-in-training and also the daughter of Centurion Ko-Rel. While considered mischievous and having a few demerits on her record, she's also regarded as exceptionally bright with great potential for a career in the Corps. While her father is officially unknown, it's suspected that it might be Star-Lord due to his previous romantic relationship with Ko-Rel during the war.
While Nikki does exist in the comic books, this version has various powers and was also born in the far-future of the 31st Century rather than the modern Marvel era. And rather than ever being part of the Nova Corps, she was rescued and later joined the Guardians of the Galaxy.
Richard Rider
Born on Earth, Richard Rider is the former acting leader of the Nova Corps after being promoted to Nova Prime by the Worldmind itself. He would lead the Nova Corps and other allied factions in the Galactic War against Thanos and the Chitauri, which eventually ended in victory. Afterward, Rider primarily focused on rebuilding the Corps' strength and took a political role in galactic affairs. He's since been declared absent without leave (AWOL) for several years and it's unknown who's currently running the Corps in his stead.
In the comics, Rider was made Nova Prime after Rhromann Dey recruited him to defeat Warlord Zorr and save Xandar. He'd also lead the Corps into battle for various wars and crises but has been replaced as leader, gone missing and even expelled numerous times for a number of reasons. What caused the video game version to go missing is largely debatable.