Ultimate Clock

Ultimate Clock is a screensaver that displays a clock. The clock is placed in the center of the screen showing the time in a funny way.

The program includes lots of types of clocks to choose from. You can choose only one of them or set the program to randomize them. They feature original themes like math clock, whatever clock, pool clock, funky clock, to name but a few. They all look very attractive, with different background colors and themes. From the settings menu, you will also be able able to select the resolution and set it to display the second hand or not. If you want you can also add sounds to the clock like the second hand sound, or set the clock to chime every hour, quarter, half of an hour, etc.

Unfortunately, the screensaver doesn't include music or transition effects between one clock and the other. It would also be great if you could select the transition time between them and choose your favorite ones.
In short, Ultimate Clock is a good choice when looking for a clock screensaver since it offers plenty of options and variety, so you won't get tired of it soon. Besides, it is completely free.