There's a ton of anime I have which I haven't completed, and although I have only a small collection, choosing is still pretty hard, so the list will probably be changed often. But for now :
1. Clannad (both seasons)
2. Higurashi No Naku Koro Ni (both seasons)
3. Angel Beats!
4. Da Capo (all 4 seasons)
5. Darker Than Black (both seasons and gaiden)
6. Toradora
7. Spice And Wolf (both seasons)
8. Code Geass (both seasons)
9. Hayate no Gotoku (both seasons)
10. Vampire Knight (both seasons)