In Marineford Whitebeard acts as if he's retarded and just keeps trying to earthquake Teach even though it isn't working. In manga, Whitebeard only needs one try to understand how Blackbeard's power works and to put him down with his bisento alone.
When Akainu fights Whitebeard he blows up half of his head in the manga; in the anime he simply burns part of his moustache.
When Mihawk was about to send a slash to Whitebeard nobody gave a shit; only Doflamingo questioned him while laughing. In the anime everybody is interested and Hancock pronounces a cringy speech about him.
In manga, Perospero didn't even need his devil fruit to submit Pedro; instead, he easily put him down with his physical strength alone. In the anime, on the contrary, he immobilizes the mink with candy around his neck.
During Dressrosa Usopp cut Trébol in three parts and completely destroyed his body once he fell on the floor. Trébol then behaved like a logia to recompose himself. This small filler completely altered the nature of the Beta Beta fruit, which turned out to be a "logia in disguise" because Trébol used his paramecia to create a mucus body.
Still in Dressrosa, there's this line where Bartolomeo speaks of Zoro and states that he's considered the vice captain of the crew. The anime ignores an important part of this sentence in manga, since Oda adds a "(by me)", indicating that it's just a made up idea Bartolomeo came up with.
In the anime, Doflamingo shot Corazón many times. In the manga he only shot him twice; this is important because it follows a pattern: he shot his father one, Corazón two, and Law three times.
In Sanji's flashback, Zeff eats his own leg in order to survive after giving our cook all his food. In the anime he sacrifices his leg in order to save Sanji from drowning.
If I recall correctly, every middle finger in manga has been censored in anime.