True. I think the majority of shipping wars are harmless fun and they don't really bother me, but there are lots of series where the MC has strong feelings for two or more characters and you genuinely have no idea who they are going to end up with. 3i3h2y

This is very rare in shoujo. It's predominantly a genre for escapism so, while there's a love rival(s) in almost every series, he/she is only there to create drama or jealousy and in some way show how much the canon couple are meant to be together. While some readers may prefer the love rival (who is often manipulative or otherwise unlikeable) it's pretty obvious in 99% of stories that he/she has absolutely no chance. That being said, Cat Street may not be for you, it's a little borderline.

I would like to second Kanata Kara, which is one of the most memorable shoujo manga for me. Although the guy has long hair and the MC may be considered plain, and the art might be outdated, I hope you will give it a try anyway.

The manga has some action/adventure/fantasy in it and the story actually does give the protagonists a fated connection, which also works as part of the conflict (and I think pretty much fits what you said about being something external, having them overcome it together, etc.). XD Other than your preferences, I also have to point out that there's a mildly huge cast of characters that you come to like (including

"bad guys" who turn good ), the length of the series is just right (IMO), and the ending is satisfying.

Akagami no Shirayukihime sound like one you would like.

you could also try
Kurenai Ouji -though its shounen not shoujo the main focus is romance

Soredemo Sekai wa Utsukushii -TONS of fluff in this one

Beast Master -short but very cute romance

[img]http://24.media.tumblr.com/3b280fafb72cad0f718be64368e64ca7/tumblr_myylzmuiY41rw3pzao4_250.gif[/img]
Like educational manga? take a look at Ed U. Manga's list of manga here

SOREDEMO SEKAI WA UTSUKUSHII it is cute, the boy is a damaged child, but a genius king as well who fell in love with nike the princess of rain with a mysterious power. It is stilll ongoing

All of them are my favorites, I think they match your description.

p.d Hana to Akuma has a bittersweet ending, I personally didn`t like the ending, but is up to you if you want to read it

Horimiya are both shounen but have very shoujo-like feels to them... especially Horimiya -- and is also very well known for giving lots of diabetes. 😀

MAYBE Koi Dano Ai Dano. I'm an avid shoujo reader but this is one of my favorites, if not my actual favorite. Great heroine. It is heavy on comedy, though. But give it a try anyway ^^

Love So Life will make you end up in the emergency room with all its adorableness XD

lots of one-shots come to mind, but being one-shots they aren't that memorable lol.

WEBTOONS ヽ( ★ω★)ノ

Hana Yori Dango
Cat Street
Mars

I'm super picky about my shojo romances, and this is one series that I kept ignoring because the preview just didn't appeal to me, it sounded like such a typical shojo, but then I had the chance to read the first chapter and have watched about 13 episodes of the anime and I feel confident in recommending it.
It's Mars