When a person who under goes extreme depression/anxiety, loses control, a person will become a demon consumed by darkness. Luckily there are those devoted to hunting those demons.
Boy meets monster while taking shortcut home from school, is rescued by a girl with a gun. Monster gets away. Later on, girl makes contract with boy and uses his soul energy to make a big gun and kill the monster.

Ninomae Iko, has lived in a house of only her dad and brothers, who all practice kendo. Looking to become a little more girly, she transferred to an all girls' school. Here, rumor has it, a magical cup filled with red wine will grant any wish if your blood is dropped into it.

Note: Plenty of pantsu moments.

In the midst of a terrorist attack that kills all his classmates,Tohru Kuroe knows the chances of seeing yet another woman die makes Tohru pick up an abandoned gun - The beast awakens; taking over. When Tohru comes to his senses, he finds he is now a killer. Finding out he was genetically engineered to be a killer, his codename is D-17, Tohru continues his 'normal' life amidst challengers threatening his life and those around him.

From Horobi no Michi:

Clockworkers- mechanical men, created during the war as a weapon to kill as many as possible. That war may be long over, but rogue Clockworkers are still roaming about, spreading fear and death wherever they go.

Machina's a member of the CWA, an organization dedicated to the destruction of these rogue robots.

Along with Deus, her Clockworker partner, she travels the country in pursuit of these dangerous robots...

Makoto Niwa moves to live in the city and meets his first cousin Erio Touwa at the house of his aunt Meme Touwa. Erio is no longer enrolled on the register of the school and is constantly wrapped in a futon. Erio claims that she is an extraterrestrial life.

The Vampire Bund, a peaceful island nation of vampires off the coast of Tokyo, ruled by Princess Mina Tepes, has seen its share of conflict and turmoil. Yet there are times of relative tranquility when the Bund is a popular tourist destination.
When two teenage tourists visit the Bund and are unexpectedly turned into vampires, they appeal to Mina and her loyal lycanthrope bodyguard, Akira, for help. Their only hope is to find a cure to reverse their vampirism within forty eight hours, or they will be stuck as vampires forever.
Unfortunately for them, their race against time turns into a game of cat and mouse that takes them across the entire Bund in pursuit of the one person who holds the key to their salvation.

Nishimura Akuji is an ordinary middle school student, until one day he gets a phone call from the Angel Realm. He's been chosen at random to be a Witch Trial Judge! He meets his new "master," a tiny angel named Lulu, who explains that their job now is to find the God Witch hiding somewhere in town, or risk her taking over the world. Using various methods, Akuji and Lulu have to hunt down suspected witches and subject them to decidedly embarrassing trials in order to expose their true forms. They're going to need all the help they can get before they run out of time!

From TJo:

In a world with floating cities know as Eden, a young boy named Jorrne attempts to return to Eden to be reunited with his mother. Born with the destiny of bearing god-killing powers, he is the object of Eden's attention--both as something to study, and something to destroy. Aided by a young magic-wielding girl named Elisiss, her sister Enefeaa, and a swordsman sent from Eden, Jorrne travels to find his way home and to discover the truth behind his power.

People live and then they die, but what matters is how they lived. It first starts around 1932 "she" a girl with bunny ears and a tail; encounter an old man named Jain; they lived together for a short time but they found a little bit of happiness by being together.; Time may pass but "They" continue to live even to the current present day and beyond. But what are they the beings called "EaRth" ?

The story of perverted Hakase and his computer, named E, which is actually a young girl who resides inside it!

From SCX-Scans:

Angela wakes up in an abandoned warehouse. Confused and dazed, she has no memory of her past or any concrete idea about how she got there. Through a series of seemingly inconceivable events, Angela learns that she has been chosen as the next vessel for the great demon queen. The only thing preventing the queen from taking over her mind and body is her virginity. Will Angela be able to avoid temptation or will the Demon Queen Lilion be unleashed to ravish the Earth?

A city is besieged by a group of monsters called Green.

Collection of bizarre short stories.

Satoshi and a group of his friends are on a lengthy boat ride to Kijijima when the world comes to an end – literally. A huge Tsunami wave 500 meters tall overpowers the boat and he finds himself stranded on an island and alone. Meanwhile the rest of the boat has grounded after being dashed upon the shores and soon Satoshi finds them, and sets off a struggle to survive for the passengers and crew of the ship.

From Tokyopop:
Yumi, a seemingly average high school girl, is destined to become the wife of and child bearer for Evil. As soon as her first menstrual episodes begin, all sorts of villainous cretins show up in the hopes of providing the seed for wickedness itself. In response, the forces of Good, a Buddhist priest, the Catholic church, and their attendant holy warriors rush to provide protection for the now-pregnable Yumi. But she reaches out to another warrior, a young punk freshman heartthrob who literally beats off the female population of the school with a stick. But when he sees Yumi in a vision, this cool-as-ice thug melts ... and the adventure begins ...

From Imangascans:
The sweet and the sour of a first love! Boy or girl, everyone is looking forward to that first encounter. No words can describe the nervousness and excitement felt at that destined moment! Perhaps the story of your first love, too, is collected in the First Love MALISA series. Malisa Lin's new work is filled with delicate artwork, elaborate drama, rich laugh-out-loud moments, and perfect endings. This series tells stories of "falling in love"...

Prequel of Freezing following Chiffon "The Monster of West Genetics" Fairchild

Mariel Imari is a private eye trying to become a first-rate detective to be able inherit her late father's estate. For some strange reason, the mysterious thief Vecchio is taking an interest in her. As if that wasn't enough, her old friends at Interpol and her siblings make life more troubling for her.

One day, a ronin student on his way home gave a bentou to a cosplay cat girl. Unexpectedly, the cat girl then decided to stay at his house, resulting in the two living together. But then, the girl turns out to be one of the mountain shrine's Gods…

Having to deal with the girl’s magic plus the teasing from other cats and Gods keeps the main character’s hands absolutely full. Will he ever get a break or will this “big pet” burden him forever?

Three quarters of the world is the world of the dead. The world has been invaded by phantoms. One day, a boy named Nagi finds in the mountains of scrap wood a mechanical teenage maid girl. He immediately takes her home to repair her. The first things that Elise, this mysterious mechanical maid, says is, "Good morning, Nagi." Who is this mysterious silver haired girl? The fate of the world rests in their hands.