Please note: while the C64 specs don't change anymore, browsers do - a lot. Chrome is recommended for best results.
Yeti Factories Cracktro (1987)
Rasterbars, color cycling effects, a starfield, a big scroller and a tune from Forbidden Forest: the Yeti Factories cracktro is a powerful demonstration of the 64's capabilities.
This cracktro left me speechless when I first saw it. It makes you think the Commodore 64 has far more than 16 colors. Add the masterful music and you have a piece of art that still impresses me today.