Sketcher 3D Pro (Android) app for $0.99

Sketcher3D is a 3D modeling, design, and fun physics sandbox. Create and manipulate 3D objects, plan out a space, or just build things up and smash them down!

This is the PRO version with no restrictions! (The LITE version does not allow saving or OBJ export, and restricts scenes to a maximum number of 10 objects - not enough for full-on physics sandbox fun!)