Pixel by using a computer is cool, but the idea of putting blocks on a raster is an old childgame! For 40 years a small company sells a game, which is called ministeck. Check the company page www.ministeck.de to get an idea of the purest way of pixeling or check the ministeck simulator to ministeck online.
A lot of Mario Bros. stuff has been submitted to the gallery. It looks like video games are everyones favourite. Some patient dude rebuilt many classic game maps, nice for remembering and inspiration.