When you get right down to it, this is actually a pretty conventional slice of life/sports anime. The characters are charming, their motivations are clearly established and the interactions between them are pleasantly satisfying. The comedy is gentle but amusing and well-timed. There's nothing that really pushes the boat out here.
...with the exception of its total, straight-faced commitment to a fantastically, spectacularly bizarre premise, which has forever enshrined Girls und Panzer as a personal favourite of mine.
It's a perfect example of everything I love about anime in general. Where the hell else are you going to see this? Someone sat down at a conference table somewhere and pitched a 'High school sports comedy/drama where the sport is painstakingly accurately depicted WWII tank battles', and then the guy on the other side of that table said yes!
And then they made that show!