This is an incredibly difficult decision for me, but I'll have to land on Ghost in the Shell: Stand Alone Complex. It's probably the single most intelligent and well crafted anime of all time, and the soundtrack is freaking amazing.
In that case, definitely Yu-Gi-Oh. And I am referring to the original before everything became perverted with GX and 5D's. Platinum beasts can wipe my...Woops! This is ZD! Let's keep it PG for the children!
I like Naruto, mainly for Part I, then I would have to say Bakuman. I love a story about the inner workings of manga making! As for anime, I would Cowboy Bebop, Fullmetal Alchemist, Death Note, and Durarara.
My favorites as of now are Death Note, Code Geass, Elfen Lied, Berserk, and Monster. I'm still expanding my horizons though; there are still a lot of supposedly great anime/manga out there that I haven't seen. I was last watching Ghost in the Shell: Stand Alone Complex but I've taken a break from watching it and plan to finish it soon, I'm really liking it so far.
My fav. anime is "Sailor Moon" i got into it whenever i was 7. my cousin showed it to me and i suddenly got hooked by the amazing outfits lol. Plus when i was that age ive never seen a show like it. I was never really big in all the japanese show until then. but that sad thing is, they stoped filming it on tv so now if i wanna watch it i have to go on youtube-.- ......but i do have some vide casset tapes....if only i had a tape player lol