Not exactly obscure but barely anyone talks about the original Fallout. It's my favorite game of all time, a true masterpiece of the genre. I've beat it at least 6 times and it never fails too hook me as soon as I start playing it.
There are other games I really love but I never see being talked about: Max Payne 2, The Godfather game, 24: The Game, the original Ace Combat (Air Combat) and Jagged Alliance 2.