1. Blue Beetle, Dan Garret, Dan Garrett, Ted Kord
Why: They have very cool histories. Dan Garret, from the other dimension "Earth-Fox", being a cop who got his powers by taking a new vitamin called Vitamin 2x. Dan Garrett (Notice the spelling difference) being an archaeologist, finding the Blue Beetle scarab in a dig in Egypt. Both "Dans" had the abilities of super strength, flight, and the ability to shoot lightning bolts from his finger tips.
Ted Kord, a friend of Dan as a child, after Dan died, Ted took up the mantle, though the scarab was lost, so Ted used his skills in technology to fight crime. One thing he had was an aircraft called The Bug.
Jaime Reyes a teenager who found the scarab in a parking lot, near his fathers garage, brought it home, and when he went to sleep, it attached itself to his spine. He then discovered abilities very different from the abilities Dan had. The scarab was able to wrap a exoskeleton suit around Jaime, and several parts of that suit was able to transform into high-tech weapons like a sonic canon or a pair of wings or a jet pack.
2. Booster Gold
Why: Time travel is cool. Michael Jon Carter, is a man from the 25th century who stole some gadgets from a museum including the Legion of Superheroes' flight ring, and the Braniac's force field belt. He then used a time machine also in the museum to travel back in time, and gain fame and wealth.
3. Animal Man
Why: He can gain the ability of any animal, do I have to say anything else. Buddy Baker encountered a crashed spaceship while hunting, and gained the abilities of any animal.
4. Static and Gear
Why: If you've seen and like the Static Shock TV show, you know Static and Gear are a very cool teenage duo. Virgil Hawkins gained the ability of electrokinesis and to control electromagnetism when he was pressured into joining a gang and brought to the docks when a large gang war broke out. When the cops arrive they throw experimental tear gas (in the show they shot a canister full of an experimental purple gas) and that begins to transform several teenagers there. Virgil then becomes the hero Static. He also appeared on the show Young Justice. He had a different origin, and even acted heroic after getting the abilities, but he hadn't become Static yet.
Richie Foley was a friend of Virgil's and only existed in Static Shock. Several years after the gang war dubbed "The Big Bang" several people begin to transform later then everyone else. Richie is one of these and gains a genius level intellect, so he invents a super computer backpack, and a pair of rocket skates.
5. The Teen Titans
Why: If you've seen and like the Teen Titans TV show, you know the Teen Titans are a very cool team. Very similar to the team Young Justice, it is also led by Dick Grayson, the first Robin, and contains several other young heroes.
Dick Grayson is the most awesome Robin, becomes Nightwing one of the coolest heroes, and even was Batman once. Nightwing and the Robins, Dick Grayson and Tim Drake appear on the show Young Justice, where unlike the comics, Dick did not lead the team.
Garfield Lynn was bitten by a green monkey as a kid which infected him, causing him to grow a tail, and green fur all over his body, but also granted him shape shifting abilities. He used this ability to become the hero Beast Boy. He also appeared on Young Justice but with the alternate origin of when he was sick, the super heroine Miss Martian gave blood, he gained his abilities.
Koriand'r the female alien who took refuge on Earth and became the super heroine, Starfire.
Raven is a half breed with her father being the inter dimensional demon, Trigon. This grants her several abilities that she uses to become a super heroine, but occasionally will become evil because of her past.
Vic Stone, the son of two S.T.A.R. lab scientists, who was mutilated by a monster from another dimension, because of a portal opened during an experiment.