I'm looking for a new manga to read... can you please recommend a one shot romance/ comedy manga...

umm, a one shot?

Well this has around four chapters but it's still pretty short
its called last game, its about a rich successful guy in school constantly coming second place to a girl and getting annoyed over it, its pretty good, cant think of any other romance one shots right now
link - link

There's also a one shot called "Good Ending" It got turned into a series after the one shot became popular but you can just read the one shot
link- link

I don't really know any romance/comedy one shot's but i do know a one-shot mystery anime called ''$100 is Too Cheap''. You should be able to enjoy it, since it's quick to read and it's pretty wel put-together.
Read it here: link

Mangahere.com

Nekomori <3333
about a guy who can see the door to everyone's heart.
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The honeybee earl and the flower dress <33
about a seamstress who was about to get arrested gets abducted by a nobleman who wants her to make a wedding dress for his sour fiancee.
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Celeste blue <3333
about a popular boy who thinks people and love are bothersome, who gets stuck tutoring a girl.
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Itazura ouji <333
because of her father's promise to his boss, mayuri has to meet the president's son.

These are some that I like. the hearts on the end of the title are how much I like them (4 being the most, 1 being the least)
Sorry that my descriptions are lousy.

I hope you like these. :)

How about Love Laboratory? Well, its actually a collection of one-shots: Love Laboratory, Merry Kiss, Perfect Doll, Twinkle Twinkle and Cupid's Love Arrow. I read it in mangahere so it should still be there.

Love Laboratory
The chemistry club invented a special hormone potion. Each bottle cost 500 yen. Riko-chan's boyfriend, Yuuki-kun himself is extremely cold towards love. Riko-chan hopes to move their relationship one step ahead, but in the end...?

Merry Kiss
Saya-chan, a beautiful model was partnered with Natsu, the #1 lusted after celebrity in order to make a passionate ad campaign. Amidst the fake kissing scenes and contrived love scenes, will the two models fall inlove?

Perfect Doll
Before they got separated, Kenji's father told him to go to Japan and to hide his identity as a puppetmaster else the black master might come after him. Renji swore he would and he intend to keep it, but now students in his school are turning up missing, and when they do come back, they are lifeless, as if their soul has been taken from them, like a doll. So now he awakens the perfect doll his father had left him and hopes to solve the mystery behind what's happening.

Twinkle Twinkle
Student by day, mysterious thief Star Drop by night. Mashiro must steal all the treasures of Reira to open the path of the old city where she believes her father is.

Cupid's Love Arrow:
She was the resident matchmaker, until he came. A transfer student claiming he's a fortune-teller and can help girls with their love problems. Trying out one of his spells to see if it'd work, Aya accidentally summons Mira angel-in-training to their world, and she learns the truth. Now she knows why he was such a good Cupid, he was the read deal himself!

(Plot summary taken from myanimelist.net)
Hope this helps ^_^

Hmmmm... I don't know a "one shot" romance/comedy, But Blackbird is an AMAZING romance/comedy. I highly sudgest it if your 14+!

Mamotte! Lollipop. The first manga I ever read.
It's about a girl named nina who swallows a pearl that is used in a magic examination test. groups of wizards try to capture her but twocute boys vow to protect her and stay by her side until the test is over.link

Shinrei Gakuen Koihenge - link

A girl has the ability to see evil spirits who eat the soles of bad humans. She sees them following a boy in her school and tries to help him. Pretty good, not as serious as it sounds

Ok 2 manga I SO recommend!
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1. Girl got Game/Power!!- In this Kyo's father forces her to cross dress as a guy so she can fulfill his dream of becomeing a pro basketball player, until she falls for a guy on her team, she deceives everyone about her sex until a little accident occurs.

2. Imadoki!- In this there's a new tranfer student at a school full of rich kids event though she got in by a test, she meets a man who has never had a true friend, or never been in love, until he meets her, but his family owns the school
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To read this, I recommend buying the books, or reading them online for free at www.7manga.com or www.mangafox.com , though I prefer 7manga. Both websites are FREE and give the complete anime series! :D P.S Neither of these have been turned into live action yet D:!!!