I’m not really sure exactly what qualifies as “surprising” in this context, but I guess the current play-by-forum game I’m running would qualify.
The game just popped completely out of nowhere directly into my head while I was in the shower. Hard sci-fi, survival horror, strange mysteries to solve when your failure could, in theory, mean the extinction of the human race. No pressure then.
The game is the same one I mentioned earlier that is using the Traveller: Classic system. I was quite surprised by just how simple it is, yet how in depth it goes. One generally tends to associate modern games with a trend towards simplicity and older games (like AD&D with THAC0 and the like) as complex, but Traveller: Classic, published before I was born, really stands up well as an example of what you can do with a simple base mechanic. I was honestly expected some complicated mess of rules and was pleasantly surprised.