There is no way I can begin to attain the level of awesomeness that is this post HERE by iam_space  - so go there immediately if you want recs and links for Hawaii 5-0. 

But in the interest of having all my faves at my fingertips, here are the Hawaii 5-0 fics that have meant something to me.  Listed pretty much in order of how I read them.  Rating and Pairing listed after title/author. ( Favorite Hawaii 5-0 Fics )