One I can think of is The World of Golden Eggs.
Aku no hana
Angel’s egg. Though it’s more so the expressions, color pallet and overall vibe that is unique rather than the animation itself (for its time the animation is pretty normal looking).
I thought Ping Pong : The animation was pretty unique. (so unique some of my friends wont watch it because of that and while I dont watch sports anime, I loved it)
I didn't watch Ping Pong but Arc did. I would check it out sometimes because the animation style was so different.
Super Milk-Chan. It feels more like your average American adult comedy, but still feels quite refreshing to watch.