It's a good example of extraordinary detail in design and animation around mechs/military vehicles, cityscapes, and retro UI designs, plus Oshii's proven directorial chops.
I also quite like the plot, which is an unexpectedly serious look at things like the JSDF's case for existence and the danger of military/intelligence bureaucracies to democratic governments.
Someone else mentioned
Satoshi Kon, and i strongly second that. Every film he made was amazing. Also, if you want to see Mamoru Oshii (director of ghost in the shell) getting real artsy in his debut, check out Angel's Egg: https://youtu.be/YopWyb75G7o
For me at least, that movie's like a bug bite i can't stop itching.
Not sure if "iconic", but I recommend Millennium Actress for an interesting way to weave a story which goes through the evolution of the Japanese film industry.
The screenplay was written by Sadayuki Murai, who put a unique touch on whatever he worked in (he also worked with Satoshi Kon in Perfect Blue).
Also not a film, but I found "Mōryō no Hako" (a short series adapted from a 1995 book) worth watching: at the heart it's basically a crime story, but the execution, with some "hallucinated" scenes, and also the characters are interesting.
Metropolis (2001), directed by Rintaro with screenplay by Katsuhiro Otomo (the Akira director). Phenomenal set illustrations, unusual character animation that intentionally harks back to the 1950s or earlier, and a fab soundtrack. The plot isn't the strongest and the aesthetic is divisive - I know some people really don't like it - but if it's your kind of thing, it's glorious.
