Ok, searching through FF.net (going backwards because most of the good fics were written ages ago) I found this little gem which I've read before but completely forget to recommend. Silly me. Check out
Father and Son by Misanagi, it's a brilliantly written piece about Bunta's thoughts on Takumi as he waits for Takumi to come home.
Another fic also focusing on Bunta and Takumi is
In the Name of the Father written by ClockworkDucky which focuses on how Bunta deals with being a single parent and shows little snippets of Takumi as he grows up. Really well written, beautiful depictions and Bunta is perfectly portrayed. There's only a handful of fics that portray Bunta just right and this is one of them.
I'm going to recommend something that others might not agree is a good fic, even I have mixed feelings about this one, but it has a certain charm about it that makes you just love it. It's called
Love Life by Rantsuki17 and although the characters can be awfully OOC (especially Ryousuke) and I can never imagine Takumi slapping Natsuki, it's still rather sweet and has it's funny moments. It's a RyouTaku and a KeiTake fic, and although it could use some serious editing and sometimes it is a bit difficult to read, BUT it has potential and the basic plot is good. It needs a little tweaking, but other than that, I do recommend you read it so please don't give up on it, it does have it's moments when it's a good fic so please don't be discouraged by the writing style.
Have a read of
Meet the Parents by Rill. I thought this one was cute. I recommend fics by Rill alot and with good reason too (it's brilliant writing and it's a RyouTaku fic...what more can I say?)
I think that's it for now.