My name is Mihai Gabriel Ailioai, and i'm the developer of Marble Arena 2, a marble game based on the marvelous Cube 2 engine. I wasn't really sure if i could post any info here being that it's not one of the official games supported by this community, but hopefully it will be ok and my post won't be deleted :)
It's a very bright and colorful game, available for PC, Mac and Linux, and it keeps pretty much all of the editing power Cube 2 has, but has a layer of GUI on top so that people don't have to use the console at all, hopefully making it more newbie friendly.
It has 50 official levels, and we've released another 22 maps ported from Marble Arena 1, and we also have a nice little community of people creating their own levels. Nothing near what i've seen here, but hopefully we'll get there someday. It's based heavily on physics, there's no shooting or killing, although we have a nice lightning bolt shield powerup that could slightly impress the killer in you :)
Check it out, you might like it, and who knows, maybe even be convinced to create some levels for it :P
Edit: March 1'st 2012
New version released. It includes 32 new levels, autosave and ability to customize controls, and what was requested the most around here: working console and custom scripts. Have fun !