Oh man, this is hard for me to choose!
Story-wise: Higurashi no naku koro ni and ni kai.. Rei I'm skeptical on because it's so far full of fillers and just when I was getting excited about the first arch in season 3.. It turned around and disappointed me >__> I just love how everything pulls you in to the story, it's confusing at first but the confusion makes you want to watch more until everything is answered.
Artistically- Paprika and Arashi no Yoru ni. One is full of mind-blowing detail, while the other has a very soft playful look that keeps an old traditional art style, but at the same time has the new modern look tied into it.
Characters and story- Princess Tutu. Despite the name and first appearance, this is definately a case of 'Don't Judge a Book by it's Cover'. The plot is very engaging and keeps finding ways to keep you hooked til the very end, the characters are all so fun and interesting, and I love how it incorporates the old with the new. Especially the classic music. Everyone knows the music, but the way it's put in the series always puts the proper emotion. Bringing old folklore, fairytales, and ballet classics and making them new and exciting is another thing I love.
It's a great anime for most anyone, even guys can enjoy it thoroughly.
Humor- Ranma 1/2 and Sayonara Zetsubou Sensei. I seriously can't stop laughing in either of them. The jokes are always funny! And in Zetsubou I have to pause a lot to see more jokes, but they're always funny to find.
cuteness- Potemayo. I think I might have exploded from the cute when I watched it....
Other's I've been amazed by... Fullmetal Alchemist (so many emotional moments) Grave of the Fireflies, Angel Sanctuary, Phoenix, Blackjack