[timeforcomputer]

Arnold is very influential especially in "Russian math" pedagogy/philosophy, which could be contrasted a bit with "French math" where Bourbaki was very influential. I think anyone interested enough to read the Bourbaki article might be interested in reading about him since his wikipedia page has a few references pointing to interesting discussions about Bourbaki's influence. I should have mentioned a little details in the original comment, sorry!

[zyklu5]

Not to mention the kind of mathematician that the Fields medal is poorer for not having as an awardee

[timeforcomputer]

Also not to mention that he has written many great textbooks on top of his research work. I would recommend anyone in an intro or second mostly-methods-based DE course to read his Ordinary Differential Equations. He doesn't entirely avoid useful methods (as I recall) but the approach was extremely different to what I had seen before, but so natural (pointing at geometry and topology, immediately discussing vector fields and a nice notation for flows in the beginning chapter).