Alright, list time.
->Any Miyazaki, except Porco Rosso. Well, see it anyway, its still Miyazaki, but its his weakest work. But especially makes sure to see Princess Mononoke. Its. A. Damn. MASTERPIECE!
-> Paranoia Agent. This show really pulls off so much whilst being so surreal. And it doesn't overstay its welcome, like so many today.
-> Hellsing and Trigun. Both based on managa, and both differ from their source matter. However, they both look fantastic and are well-written, and have top-notch action.
-> Akira. This one is older, but it really set a standard.
-> Ghost in the Shell: Stand Alone Complex (1 and 2nd gig). This show looks beautiful and really the plots in both play out really well. For some reason, I NEVER got into the first movie and its sequel. In those two, all the philosphy was awkwardly forced for some reason.
-> Code Geass. This one really surpised, as I was expecting some kind of shallow nonsense that you get from alot of anime these days. However, it pulls off the mecha aspect well while playing a very strong plot. It covers a number of themes, including responsibilty, loyalty, perception, etc. There's a weird amount of fan service, but it doesn't really pull away from the show at all. Every battle feels important not just in the battle itself but also to the plot as a whole, and not many mecha shows can pull that off. I would say a must see.
-> Samurai Champloo. This show looks great, has plenty of high quality action, and mixes old-world japan with hip-hop. Amazing. The plot could be better, as it feels that alot of the subplots are not related to each other or the main plot in any way, but still a great show. Well, sort of...
-> I tentatively put forth Gundam 00. This show tricked me. The first few minutes had me convinced that this show would be the realistic gritty side of mobile suit war that I had yet to see properly addressed. However, I was wrong. This show does deliver, though. It effectively looks at the conflict from a variety of different stand points, and does it well. Unfortunately, the nature of the plot lends itself to what seems like a train of Deus ex Machina's. This one will be hit or miss. However, its the only Gundam show I've ever enjoyed. AT ALL.
->Ninja Scroll. This on was weird. Anyone who has seen Basilisk will get a sense of Deja Vu. Its your classic bloody ninja action movie, with each fighter possesing some unique ability, etc. However, the fights are (weird powers aside) realistically done, and it helps to remember that Ninja Scroll is old-school, and gets props for setting a standard.
I've heard good things about Envangelion, Death Note, Gun Grave, and Full Metal Panic!