A clarification…I LOVED both of the ones I've watched where he wrote the novel/manga (Madoka Magica, Fate/Zero), but he WILL play with your emotions all the way through.
Clannad…I'm hesitant simply because I know how much it's emotionally impacting hehe. If you haven't watched either Fate/Zero or Fate/Stay Night, I was recommended to do Zero first as there're far less spoilers for Stay Night in it than there are for Zero in Stay Night (seeing as Zero's a prequel and all)…plus Ufotable (studio that did Zero) is remaking Stay Night anyways, halfway through the first season at this point in time…