1. Soul Eater - Amazingly original characters, fantastic plots, great artwork, and a little fighting to boot. You can't not like this.
2. FMA (both versions) - One of the best plots of any anime. Characters were neat and the action was always fun.
3. Death Note - Amazing plot and the suspense was exhilarating. The only negative was the ending.
4. Rainbow - A story about seven boys sent to a Japanese juvenile penitentiary, their lives there, and their lives afterwards. Definitely for a more mature audience.
I've seen many others, but I don't feel like listing anymore at the moment.