Fist of the North Star and Record of Lodoss War

Angel's Egg if you're into slow, melancholy eeriness

Ninja Scroll

Fist of the North Star

Possibly the A-ko series.

Dallos (4-part OVA, but basically a film length): Mamoru Oshii makes space communism the anime.

Dragon's Heaven: Cool one-shot OVA. Mobius vibes in the art and a banger scale model opening.

Metal Skin Panic MADOX-01: Another one-shot mecha OVA. Simple plot, but a fun ride with solid animation.

Space Runaway Ideon - A Contact and Be Invoked: a double feature movies by Gundam creator Tomino. The fist one is a compilation film - the TV version is better, but that's not the assignment here. The second is one of the best sci-fi anime movies of all time. Evangelion copied a lot of stuff from this movie.

Megazone 23 is sick as hell.

Wings of Honneamise has gorgeous animation, when you boil the plot right down it's a bit "we live in a society" but it's still good

Metropolis came out in 2001 but it's got even more gorgeous animation

The Last Unicorn is an excellent film - it's western, but the animation was done by a studio that would later be hired by Miyazaki for Nausicaa

It might be cheating to keep mentioning Ghibli-adjacent films, but I also really love The Castle of Cagliostro

The Birdy the Mighty OVAs are pretty good, short and sweet - the TV anime is fine but kinda long and doesn't really add much (banging soundtrack though)

On the subject of OVAs, you gotta watch Gunbuster if you haven't yet, you will cry at the ending

The Patlabor OVAs and films are great, beautiful mecha animation and political intrigue (the OVAs+films form one continuity while the TV series and later OVAs form another)

That's all I can think of for now, although this lot should keep you busy for a while!

California Crisis is a great 80s OVA involving aliens, the CIA, and the KGB trying to get the main characters. Fantastic pastel color pallete and it's really fun and it's in one movie.

Non-anime suggestion: The Secret of NIMH. Don Bluth’s first film after leaving Disney.

Some Eastern Bloc animation:

The work of Karel Zeman (Czechoslovakia), like The Fabulous Baron Munchausen

The work of Marcell Jankovics (Hungary), like Son of the White Mare

Romania's first feature-length animated film Delta Space Mission

Royal Space Force

I very much liked Memories, an anthology produced by Katsuhiro Otomo. I didn't watch Neo Tokyo, an earlier anthology but I hear it's pretty good as well

Cyber City Oedo is a lot of fun - a three part OVA about three prisoners who are offered a chance to reduce their thousand year sentences (for the crime of being total badasses) by donning bomb collars and going on suicide missions for the cyber-police.