Depends on whether you care about the graphics or not. There are some old anime or some faithfully following the artstyle of the manga and end up looking bad to put it simply, though you might find it charming in a way.
If you don't mind poorer art, i recommend these.
Code Geass
Hajime no ippo (though the latest seasons are pretty well animated)
ping pong the animation
DeathNote
Full metal alchemist: brotherhood (important to add brotherhood)
Slam Dunk
One Outs
If not,
Yakusoku no Neverland
Steins;Gate
Mob Psycho 100
One Punch Man
Owari no Seraph
Tower of God (Kami no Tou)
Fate Zero (I do not recommend Fate Stay Night 2006)
Kingdom
Kiseijuu
Grand Blue
Bokura wa minna kawaisou
Death Parade
PsychoPass
If you are into anime movies,
Kimi no Na wa
Koe no Katachi
Gintama movie 2
Detective conan movies (there are more than 10)
And lastly some of the anime series i mentioned above has movies as well.
For now this is all I can think of off the top my head. I avoid the previous big 3, one piece, bleach and naruto because its kinda common and i imagine you probably gave it a go. But if you haven't, I can recommend one piece. Naruto was okay but naruto shippuden (season 2) starts off okay but gradually gets ridiculous. Bleach was good till a certain ark and then it went down hill, the ending was also rushed so I cannot recommend this at all.
Go nuts.