I've had a lot of fun using Nim for AOC for many years. Once you're familiar with the language and std lib, its almost as fast to write as python, but much faster (Nim compiles to C, which then gets compiled to your executable). This means that sometimes, if your solution isn't perfect in terms of algorithmic complexity, waiting a few minutes can still save you (waiting 5 mins for your slow Nim code is OK, waiting 5 hours for your slow Python isn't really, for me). Of course all problems have a solution that can run in seconds even in Python, but sometimes it's not the one I figure out first try.

Downsides: The debugging situation is pretty bad (hope you like printf debugging), smaller community means smaller package ecosystem and fewer reference solutions to look up if you're stuck or looking for interesting alternative ideas after solving a problem on your own, but there's still quality stuff out there.

Though personally I'm thinking of trying Go this year, just for fun and learning something new.

Edit: also a static type system can save you from a few stupid bugs that you then spend 15 minutes tracking down because you added a "15" to your list without converting it to an int first or something like that.