* 'The Exchange'. Last mission where you FINALLY get to kill [[spoiler:Catalina]], and with a rocket launcher no less. Made even more satisfying by the difficulty; you start with no guns and there's no checkpoints along the way. Plus the news report cutscene that ends it.
* Flying the Dodo (A plane with crippled flight mechanics) succesfully. Around the city. Even to "Ghost Town", the (normally unreachable) part of the city where the intro takes place.