i highly highly recommend nodame cantabile, it's a manga focusing on a girl who has a talent for playing piano, but has no motivation and a guy, who is talented at playing the violin and piano but wants to become a famous conductor. although it the manga focuses generally on these 2 characters, it also follows the development of musical talent of the friends of these two as well.
while it is mainly about them trying to reach their goals, it's also really funny and romantic too.

others i highly recommend:
Glass Mask - acting
Beck - music: guitar playing and singing
Ashita no Ousama - playwriting and directing
Crimson Hero - volleyball
Prince of Tennis* - tennis
Air Gear - air-trecking, kind of like rollerblading but much much cooler and dangerous.
The One - modeling

sorry if some of these have already been mentioned, i couldn't remembers which ones have and haven't when i typed this

in almost all manga's, the Characters have a talent/skill, and improves it through hard work and training. The manga's you listed however do focus on the talent and hard work as the emphasis of the story.

Hollyland, is a manga about a weak little kid, who was constantly bullied, and now has really low self-esteem, so he trains to become stronger so that he won't be bullied anymore

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CoCo wants to Go GO

Vagabond might be up your alley.

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hikaru no go

How about the talent of hard work?
History's Strongest Disciple Kenichi

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