Gaggy Gagsworthy

Gaggy Gagsworthy (yes, that's his real name) use to be circus tightrope walker. However, he lost that position to the Flying Graysons (Dick Grayson and his parents) and was forced into become a clown, which he really hated. During an act, he attacked one of his fellow clowns. This got the attention of the Joker. Gaggy, who was willing kill people for a laugh, became the Joker's answer to Robin. The duo of the Joker and Gaggy committed various crimes before Batman and Robin sent them to prison. However, the Joker was declared insane and was sent to the Arkham Asylum, thus leaving Gaggy alone in prison. Gaggy was released and went to the Joker's old lair only to discover that the Joker had a new sidekick: Harely Quinn.
Abilities
Gaggy has a variety of abilities. He is extremely agile and is shown skilled enough  to compete with Dick Grayson. He is also a skilled fighter. He has sonic screaming powerful enough to break mirrors and knock out Catwoman. Gaggy also carries around various gag-based gadgets à la the Joker.
References
http://www.comicvine.com/gaggy/29-51451/.

Mr. A

Mr. A is a superhero created by Spider-Man creator Steve Ditko. Mr. A is an objectivist superhero. His name is reference to the phrase "A is A". Many people think he was an indirect influence for Rorschach from Alan Moore's Watchmen.

Rex Graine is a newspaper reporter (for a newspaper Daily Crusader). As Mr.A, he wears metal gloves and mask; a fedora hat and a detective suit. No origin is given, which begs the question why he dresses up like Mr. A if he acts the same way regardless of if he is Mr. A or Rex. He has a half-black and half-white calling card.
Mr. A believes in pure good and evil without any moral grey. He believes in objectivism. He is willing to kill people if an innocent life is at stake and does so mercilessly. He only feels for "the innocent and victimized". He constantly rants on and on about his philosophy even when it means grinding the story to halt (much to the readers' annoyance).
A typical story has someone doing a small crime. Then, they do more crimes. The crimes escalate to the point that the person tries to cover their crimes or run away. The person tries to justify what they are doing without actually blaming themselves. Then, the story ends with Mr. A confronting them and telling them about how they are guilty. Other times, the "story" is just Mr. A denouncing people for having "compromised their values" and debunking their arguments.

My sources was:

• http://en.wikipedia.org/wiki/Mr._A
• http://www.dialbforblog.com/archives/297/
• http://tvtropes.org/pmwiki/pmwiki.php/Main/MrA
• Scans of an issue of his comic, but I can't find the link to it

Professor Ojo

Professor Ojo was the son of an assistant at a nuclear facility. Ojo's father was exposed to radiation causing Ojo to be born without eyes. Naturally, Ojo grew to hate atomic enegry. Being a genius despite his handicap, Ojo built a machine to allow him to see. He became an associate of the League of Assassins. He stole an "atomic submarine" only to be stopped by Richard Dragon and Ben Turner (G.O.O.D. members). Turner tried to confront Ojo because one of Ojo's lackey killed Turner's wife. However, Ojo brainwashed Turner into being the assassin Bronze Tiger and sold off his services. Ojo placed a giant flying eye over Star City. Green Lantern Guy Gardner destroyed it after Green Arrow and Green Lantern Hal Jordon failed to do so. He had another flying eye and used it to attack the Arkham Asylum thus freeing the villain Crumbler (real name Alexander Tuttle). Ojo teamed up with Alex so they could attack a nuclear power plant and show the world the horrible effects of radiation.  However, Green Arrow and Green Lantern stopped them.
For those you don't known, "Ojo" is the Spanish word for "eye".
My source was http://en.wikipedia.org/wiki/Professor_Ojo.

Sublime

In my posts about the U-Men and Xorn, I mentioned a villain called "John Sublime". So, I decided to do a post on him since most of you likely have no clue he was.
Sublime is a sentient bacteria and one of the first lifeforms on Earth. When multicelluar lifeforms appeared, he discovered he could possess them. However, mutants (like the X-Men) were immune his powers thus being a threat to him. It is hinted he started the fear of mutants (which if true would completely miss the point of the X-Men mythos). Sublime founded the Weapon Plus project by taking over a human body and taking the alias "John Sublime". The idea of the program was to create living weapons. The phases of Weapon Plus are referred to as "Weapon [Roman numeral]" such as Weapon V or Weapon XI. However, Malcolm Colcord caused Weapon X to be independent program. John Sublime founded the "TransSpecies Movement", which focuses on humans transfering mutant organs in their bodies thus giving them super power, and the U-Men. The X-Men discovered Sublime's "mutant farms" and tried to stop him. Sublime tried to buy Xorn from corrupt Chinese officals. Emma Frost seemly killed Sublime by accidentally dropping him off a building. However, Sublime survived and went back to leading Weapon Plus. Weapon XII-XV were Sublime's attempt to make genocidial mutant hunters that would look like a "Saturday morning cartoon come to life". Ultimaton (Weapon XV) was the only loyal member and was killed by Wolverine. Sublime made Xorn / Magento take over New York City via his mental powers in "Planet X". Xorn / Magento was killed by Wolverine. Chamber tried (and failed) to kill to Sublime. After "House of M" and most of the mutants losing their powers, Sublime tried to kill the X-Men with an army of robots and failed. The mutant haters Lobe, Thug, Verre, Burst and Bouncing Betty claimed they were working for Sublime.
Sublime has various powers. He can possess people. Under normal conditions, he cannot possess mutants. However, he can bypass this if the mutant is using the fictional drug Kick. He can control minds and enchance the powers of his host. He can cause his hosts to regenerate, which is how he can survive so many near-death experiences.
My source was http://en.wikipedia.org/wiki/John_Sublime.

Arm Fall Off Boy

The Legion of Super-Heroes comics have a recurring gag where the members interview potential new members that have moronic powers or an inability to use them correctly. One of these rejects is Arm Fall Off Boy. 

Arm Fall Off Boy's origin is unknown. Matter-Eater Lad claimed Arm Fall Off Boy got his power by holding onto the anti-gravity Element 152 (which, based atomic mass given, should be Europium) too long. However, he may have been joking. As you probably guessed from the intro, Arm Fall Off Boy tried to join the Legion and failed. 

In the Zero Hour timeline, his real name is Floyd Belkin and goes under the name Splitter. It is also stated he from the planet of Lallor, making Matter-Eater Lad's claim seem more plausible since most of the planet's inhabitants are normal people. In Legionnaires #43, he tried out for the Legion and was among of the finalists. However, he was rejected for literally falling apart during the last test. Later, he was seen as a member of the Heroes of Lallor (Lallor's main superhero team). 

Arm Fall Off Boy easily has one of the dumbest powers ever. He can detach his limbs, which seem to harden, and use them as clubs. He can reattach them as well. Unlike the M. F. Enterprises Captain Marvel, he cannot fire him like a missile and has to use his other arm. 

My sources were:

• http://en.wikipedia.org/wiki/Heroes_of_Lallor
• http://en.wikipedia.org/wiki/Arm_Fall_Off_Boy

Armless Tiger Man

Yes, this is real.

Hertz (no first name given) was a German Factory worker. However, his lost his arms when they got caught in machinery. He learned how use his feet and teeth to compensate for his lack of arms. He gained a hatred of machines. During World War 2, Hertz was sent to sabotage American factories. He was defeated by the Golden Age Angel and was sent to prision. Later, in Incredible Hercules issues 129-131 (which takes place in the year 2009), the Armless Tiger Man is seen as one of the villains in the underworld attacking Hercules, Amadeus Cho and Aegis.

My source was

• http://www.comicvine.com/armless-tiger-man/29-41610/ 
• http://www.comicvine.com/incredible-hercules-the-descent/37-158660/ 

Key

Golden Age

The Key was an originally one-shot JSA villain. He was a major crime syndicate leader with agents across the world. He was being chased by the JSA. So, he ended up jumping out  a cable car and seemly to his death (he hasn't been seen since).

Modern Age

A new and seemly unrelated villain named Key appeared in Justice League of America (vol. 1) # 41. He was a chemist that worked for the villain team Intergang. Later, he used "psycho-chemicals" to allow him use the unused 90% of his brain (the writers still thought humans only use 10% of their brains despite that not being true). This allows him to use 10 senses that uses to commit crimes. He uses a Key-Gun and has henchmen called "Key-Men". He had several clashes with the JLA, but just disappeared. He returns two years later in real time. He was apparently in a coma due to the chemicals, which now changed his appearance (as seen above) and enhanced his mental powers. He broke in the JLA's HQ and trapped the JLA members into various fantasies via "a dream-like flu" he made. However, Conner Hawke (who wasn't there when Key did this) stopped him by beating him up when he was distracted. Key was thrown in the Arkham Asylum, where he unsuccessfully tried to get Batman to kill him (claiming he was trying to "escape life"). In the aftermath of  the storyline "World without a Justice League" (see JLA #120-125), he was sent to the "dream realm" (not to be confused with the Dreaming). He later escaped by unknown means. The  Key was seen in a special prison cell, which negated his powers. He somehow escaped off-panel. In Final Crisis, he was a member of the Secret Society of Super Villains. In The New 52 universe, he started at riot at the Arkham Asylum to distract the Justice League for a then-new villain.

References

http://en.wikipedia.org/wiki/Key_(comics)