What is your favorite retro video game?

I am bored so i thought lets bother BHW with useless drivel and so it goes, right now i am playing Half-Life this game has me in its spell since it cam out back in 98…. So my dumb question is……..

Taaaaadaaaaaa What is your favourite retro game?

And to be retro it has to be a title from before 2005 (totally arbitrary of course but it is MY thread and i decide what is retro and what not) I know some of you where stil in diapers but i'll bet there are some old gamers around in this…

What is your favorite retro video game?