Hana Yori Dango and Hana Kimi are my favourites, but I haven't seen many.
Nakatsu
Domyouji and Rui
I've seen the first two episodes of Gokusen and I plan on watching Nobuta wo Produce and Kimi wa Petto soon
My friend lent me One Litre of Tears and for some strange and unknown reason I started watching from episode seven thinking it was the first one
... The weird thing was that it all kind of made sense. I watched seven and eight and was bawling the whole time, sheesh it's soo sad! I've also seen the first episode (realised my mistake
) and that was really good. I had to give the dvd back to my friend but I'll find it on the internet as soon as I'm brave enough