What game is complete without music? This mod from jaidenjc contains the theme from Sonic and the Secret Rings, "7 Rings in Hand," by Steve Conte. It embodies the sound of the 3D Sonic games with its upbeat rock style and quick pace. It's perfect for any world you create in Garry's Mod, of course, but we can't help thinking it would fit especially well in the Sonic stage mod too.
From characters and vehicles to full blown stages, there's plenty of Sonic material to be found for your sandbox creations. Let us know if you plan on picking any of these up!