Bootanimations have always been a particular favorite of mine. I used to make my own bootanimations just for that added level of customization, but now I just let other designers make the bootanimations for me.
One great bootanimation that is raising in fame is the ZeldaHD Bootanimation from Bhoot.
This animation features various items from the ever popular Zelda games. You need a rooted device to apply the bootanimation, but it is a gorgeous animation either way.
You can download it from here as well as find install instructions.