Well, i kinda think of Rain

I second this!

I would have to say that Tora Kiss: A School Odyssey is a really good example of what you want. We have not gotten even close to a glimpse of the MC's true power, but we see him gradually start to use more and more. All in all, kind of exciting. Updates are slow though so you might want to hold off for a bit unless you really can't wait. Happy Reading! 😀

Edit: I just remembered that another one you'd want to check out is Blood Lad, more developed story, pretty nice premise if you don't mind a bit of romance.

First thing that came to mind was Shina Dark

maybe One Punch Man

[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

Iris Zero where the main character have great detective ability but have 'principle' of remaining in low profile so he never use it.
Angel Diary main character is actually very powerful, but she hides it so she can live a 'easy' life as a NEET.

Ruler of the Land

Well.. at the beginning the MC does not really want to fight because he hates fighting but then later on though he decides to do so.

Blood Lad is the one for you then.

I'm surprised no one said this but Servamp.
Kuro is basically extremely lazy up to the end and is also incredibly powerful. He is literally the sin of sloth loool