The bumbleball is a new puzzle element created by Skotty and Moth of Team Citruz.
If the bumbleball is outside of the players view it will bounce around every 2 seconds, making a distinctive sound when bouncing. They're *very* different to spheres, and behave differently to blue painted cubes, making them unique inthis respect.
More information is available at this link: 
The download contains:
-A normal sphere button specialized for the bumbleballs, not useable with other objects. -the single bumbleball (model and textures) -droppers for bumbleballs, dirty and clean -the .PSD file for custom textures
bumbleball supports up to 16 skins -- 'skin' values 0-15 in Hammer
No scripting is required to add a bumbleball to your map; just add one of the included dropper instances, and trigger it with a button.
Paint effects don't work properly (read: at all yet) so the bumbleball cannot be used in the same map as paint elements. Fizzlers won't just dissolve it, you have to fire 'User1' - (to be updated shortly with clarification)