For an action #anime , I'm gonna go first with Girls Und Panzer, because that tank action is too good. (Also I see that you asked the other day about anime that promote something; somehow I ended up playing War Thunder instead of World of Tanks, but still pretty effective).
I also have to say Attack on Titan. Both the titan fights and the ODM gear fights are incredible to see animated, season 4 especially.
For a #manga (though not really the anime) I'll throw out Kingdom. (While I've heard the animation improved in later seasons, the season 1 animation was really wonky, so I quickly stopped watching.) I like the historical setting, in warring states era China, and especially in the earlier arcs I think there's a great balance between seeing combat in the small scale and seeing the flow of battle overall.
Ionplasma