When the "detect physics collisions" feature is added (it's on Ash's to-do list) it'll be pretty easy to restrict bounciness for any physics object. Until then, I'd wait patiently.
Though I agree that a setting for this would be cool. Some kind of "Kinetic absorption" setting, where 0 would equal "absorb no force on impact" for super-bouncy objects, a setting of 50 would be medium bounciness for things like wood or rocks, and a setting of 100 wouldn't bounce at all on impact and basically stick to the ground (or wall/ceiling, in a zero gravity environment), like if you dropped a ball of clay.