A collection of one-shots:

Vol 1:
Magician
Fairy Tale
Cocona
Plue's Adventures Pt. II

Vol 2:
Bad Boys Song
Magic Party
Christmas Hearts
Fighting Group Mixture

From Neptise Scans:

The story follows Shintaro, the Ganma Army's #1, after he gets stranded on the wacky Papuwa Island.

From Anime New Network: Zushio was to be king and promised his sister that he would become king (on penalty of death). Unfortunately for him, his empire was overthrown and now he's a wanted man. A girl has the misfortune of running into Prince Zushio and becomes tangled in his plight. Adding to her misfortune, Zushio is not quite right in the head, but hey, at least he seems to be immortal.

The tale of Monster Soul takes place in Elfenland, which is inhabited by both humans and monsters. The main characters are a group of monsters called the Black Airs. The Black Airs is recorded as the strongest group of the monster forces in the great war between the humans and monsters.

The story takes place in a fictional world full of monsters and adventurers called Monster Hunters, who, as their name implies, hunts these monsters. The plot revolves around a young Monster Hunter, Shiki, whom was taken in as an apprentice to a Monster Hunter named Gurelli as a child. A few years after Gurelli's death, which was due to a gunpowder incident, he comes back to his master's residence, Akamaaya Town, to join the guild there. In that guild, he meets a girl called Irie and after a series of events, he finds that she is the daughter of his master. From this point onwards, they form a party to find the legendary Miogaruna, which was Gurelli's life-long ambition.

From: Easy Going Scans

Mahiro is the prince of the Mismarca Kingdom, he won't study nor learn sword skills, he is a lazy prince who only plays until late night. His Imperial Bodyguard Pariel would always scold him for his behaviour. And towards that Mismarca Kingdom an elite squad from the Demonic Kingdom Granmarsenal is aproaching. The Leader of the squad is Lunas, a warrior princess, the third Princess of Granmarsenal. All of Mismarca's vassals voiced their will to fight and bring all-out war, although there is a man who said cowardly "Why don't we have a talk with them?". What kind of fate awaits the Mismarca Kingdom and its useless Prince, Mahiro?

From Adachi's Universe:
We start with our main protagonist, Shichimi, bidding farewell as he readies for his journey into Edo (on our Earth, Edo was the old name of Tokyo before it became the capital of Japan). His mother has just died, only leaving him a walnut and a request for him to go to his half-siblings. Shichimi bids farewell to a sternly old man, who is a firefighter. We can tell this from the symbol on his cloak. This symbol is also on Shichimi's cloak. Upon reaching the town of Edo, Shichimi meets a mysterious man, who ridicules the peace of the world as an illusion.

Lakate is a man with the face of a wolf due to a curse. While traveling to find a cure for his state and the reincarnation of a woman who helped him long ago, he meets a lost young girl, Kukaru. This is where his real travel begins...

Quoted from 4dawgz (the scanlator)-
"So there's a magazine called Gelatin where various manga artists are given some coloring crayons and then told to draw whatever they want in full color. The plot for this is about a guy and a girl who go on a mission to retrieve a pair of shorts from an island... aaaaand that's it. All you'll find is a nice slice-of-life story and lovely colored pages."

Nanami Sekai gets scammed out of every penny he has, left only with a pair of boxers and a 3,000,000 yen debt. He then meets a girl, Ritori, who offers him a deal that seems too good to be true: she will take care of his debt if he will be her captain and help her with her job.

[Note]
It seems that this manga has been discontinued because the author became incapacitated during serialization and was not able to keep 2 series running.

One day, cute little Tarepanda decides to go on an adventure. But after a few bad turns, he realizes he misses home. Will he find his way back? Or will he stay lost forever?

This little one-shot is simple, charming and cute. If you like sweet slice-of-life / adventure stories, do yourself a favour and go read it!

From Tokyopop:

Having been assigned by the human elders the mission of stopping a mystical plague that has afflicted the Youkai with madness, Genjyo Sanzo assembles his team of Youkai warriors, desperately hoping that the disease will not affect them. He sets up qualifying tests that will help him determine the loyalty and worth of Cho Hakkai, Son Goku and Sha Gojyo. The team then journeys west to rid the land of madness.

The continuation of Slayers Revolution. After the defeat of Zanaffar, Lina, Gourry, Zelgadis, Amelia, and Pocota, the prince of Taforasia, continue their hunt for Rezo’s urn, each with their own motivations for doing so. Pocota to revive his people from Rezo’s well-intentioned sleeping spell, and Zelgadis to regain his former body. However, something deeper is circling around the intrigue behind Rezo’s urn, and all will come to a head in the bustling city of Vezendi...

The demon queen subdued enormous and powerful monsters and slaughtered over half of the world's population. Surviving members of the human race elected a hero to slay the demon queen, beseeching release from her oppressive rule. However, he questions his mission to eradicate the monsters: in his opinion, they too are conscious and alive, and so he anguishes over that fact. Sheila the Demon Queen became interested in him and joined his journey, hiding her identity and with the plan to kill him after she has gained his trust. Eventually, she realizes that she fell in love with the hero, and hence their journey begins...

Taking place in 1930s Japan and China, Kasumi Kenshiro (the uncle of the lead from Hokuto no Ken) is forced to leave his teaching job and settle an old gang rivalry with the help of his martial arts. Along the way, he meets the son of one his triad buddies, an old flame, and a mysterious old man who teaches him new techniques which will assist him in his quest.

This is a collection of loosely interconnected stories where the main characters are all animals, especially the tiger who is the hero of the first book.

Our hero Vash the Stampede disappeared for two years after blasting a crater onto the moon above the desert planet he saved from annihilation. But with good people and bad alike trying to track him down, he won't stay lost for long! Count on more crazy gunslinger action, new dastardly villains...and a new outfit, to boot!

Note: Nightow changed publishers to Shonen Gahosha and the series continued to be serialized in Young King Ours magazine. Due to the original publisher retaining the name Trigun, Nightow had to change the title to Trigun Maximum, which isn´t a sequel but a new name for the rest of the series. The first 3 volumes were published under the title 'Trigun' and the entire series compiled into 14 books as 'Trigun Maximum' (the numbering was also restarted when the title changed).

Won the Seiun Award at the 48th Japan Science Fiction Conventionwere for the best comic of the year.

A miniseries prequel about the encounter between Rain and Zol. This is a prequel to Immortal Rain set before Machika's birth. Machika's grandfather Zol, who works as a bounty hunter by the name of Grim Reaper, encounters Rain, who turns out to be Methuselah, the most wanted man in the world. Why did fate bring these two men together and what is hidden behind Rain's clumsy and kind personality?

From Aku Tenshi:

The world of Waq Waq is a place where machines attack the black-blooded humans, whose only defense are the Sakimori, humans chosen to partner up with the Goujin-zou, a race of machines that grow stronger when melded to humans. Shio and his Sakimori father, Al, upon entering a village, are attacked by the machines. As Al falls in battle, he leaves his son to become the new Sakimori and guardian of a mysterious young girl, believed to be god, found at the heart of the battle. Waq Waq is the story of Shio as he battles to protect what was entrusted to him by his father. Let the battle for God begin!

From Storm in Heaven:

Beat has always dreamed of being the Golden Hero of Totia. He made a pact with his best friend Ricercare (Rice for short) to join forces to annihilate the demon king in order to achieve this aim. Yet a twist of fate causes him to abandon his goals and fight alongside Rice to protect the demons. Just how will they fare against the entire nation of Totia? And can Beat protect Rice from the hero of Totia before it's too late? Cute and heart-warming, this amusing five-volume series also includes interesting side stories rich with magic and beautiful art.