Your favourite First generation game?

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So one of my university assignments (History of Interactive Entertainment) has me looking at the first three generation of console/computer games. The course overall has made me quite curious into other people's playing habits and why people play, what makes them choose one game over another that is similar or why a person choices one console over another. Anyway, said assignment has me playing a first generation game and writing about it - my experience etc. So my question to you is what is your favourite first generation game? I'd be quite interested in hearing of any particular game that you remember playing that isn't mentioned on wikipedia, as I'd love to do something in the assignment that I haven't played before for a greater experience and to not be biased with any old memories. If you are curious on the different generations of gaming there is quite a bit of info on wiki detailing the history of all seven generation - http://en.wikipedia.org/wiki/History_of_video_game_consoles