If we're including visual novels, Fate/Stay Night and Tsukihime are both amazing. I've also read Clannad, but you'd be better off watching the anime. Only read the VN if you want the Kyou/Tomoyo arcs... which most people do.
And coz everyone else is listing the anime/manga I've watched/read:
Yu Yu Hakusho
Neon Genesis Evangelion
Welcome to the NHK
Negima (manga... don't even think of going near the anime)
Full Metal Alchemist: Brotherhood
Nurarihyon no Mago (god, thats a ***** to spell)
Tengen Toppa Gurren Lagann
I made attempts at watching Hellsing, Yugi-oh and Lucky Star but Hellsings anime is terrible and it kinda put me off reading the manga or watching Ultimate, Yugi-oh starts off hilariously but Pegasus' campness, Bakura's britishness and Yami Yugi's voice end up getting old so all you're left with is Kaiba and Joey, and I've been advised to go back to Lucky Star when I've watched at least a 100 anime because the jokes are lost on you.
I'm reading through the Umineko VN at the moment (barely started)... but I don't know what to do after that Bakemonogatari, Great Teacher Onizuka, Sayonora Zetsubou-sensei, Kanokon, Outlaw Star, Cromartie High School or Black Lagoon will probably be next >_>
Cowboy Bebop! Woo!
I also like, Deathnote, Bleach, Gundam wing, Fruits basket and Prince of tennis.
Tom and Jerry is not Anime, I suppose.
My favourites WERE:-
That's about it.