I used it for about 30 minutes years and years ago and didn’t really like it but Carrot Weather for iOS fits this bill. I believe it insults the user and generally uses snarky language. That’s pretty much its whole schtick, so it’s not really a hidden feature or easter egg. I don’t even know if it provides any more accurate weather information than other apps; I think people use it mostly for its ‘character’.

Again, not really my thing but it’s featured on the App Store a lot and has won numerous awards.