The top 5 just isn't enough so here's a few extra. I'd say the top 5 plus the following should be a must see list.
Kyou Kara Maou
Almost anything from Studio Ghibli
Princess Tutu (NOT JUST FOR GIRLS! Really great storyline, totally captivating)
Cowboy Bebop (of course)
Full Moon wo Sagashite (A little more on the immature side than I usually do, but great characters and a great story)
Read or Die (For the bookworm in alll of us)
That's it folks!